diff --git a/README.md b/README.md
index 82b6f1a..dcbe856 100644
--- a/README.md
+++ b/README.md
@@ -16,7 +16,7 @@ Concept
 |     FlatDB     |      Disk     |       Lua      |
 |:--------------:|:-------------:|:--------------:|
 | Database       | Directory     | Table          |
-| Book           | File          | Table          |
+| Page           | File          | Table          |
 | Key-value pair | File content  | Key-value pair |
 
 Keys and values can be all Lua types except coroutines, userdata, cdata and C functions.
@@ -36,32 +36,32 @@ local flatdb = require 'flatdb'
     local db = flatdb('./db')
     ```
 
-2. Open or create a book
+2. Open or create a page
 
     ```lua
-    if not db.book then
-    	db.book = {}
+    if not db.page then
+    	db.page = {}
     end
     ```
 
 3. Store key-value items
 
     ```lua
-    db.book.key = 'value'
-    -- equivalent to db.book['key'] = 'value'
+    db.page.key = 'value'
+    -- equivalent to db.page['key'] = 'value'
     ```
 
 4. Retrieve items
 
     ```lua
-    print(db.book.key) -- prints 'value'
+    print(db.page.key) -- prints 'value'
     ```
 
 5. Save to file
 
     ```lua
     db:save()
-    -- 'book' will be saved to './db/book'
+    -- 'page' will be saved to './db/page'
     ```
 
 More usage can be found in the *cli.lua*(a Redis-like command line interface example using FlatDB).
@@ -73,21 +73,21 @@ Quick Look
 local flatdb = require("flatdb")
 
 -- open a directory as a database
--- 'db' is just a plain empty Lua table that can contain books
+-- 'db' is just a plain empty Lua table that can contain pages
 local db = flatdb("./db")
 
--- open or create a book named "default"
+-- open or create a page named "default"
 -- it is also a plain empty Lua table where key-value pair stored in
 if not db.default then
 	db.default = {}
 end
 
--- extend db methods for getting values from 'default' book
+-- extend db methods for getting values from 'default' page
 flatdb.hack.get = function(db, key)
 	return db.default[key]
 end
 
--- extend db methods for setting values to 'default' book
+-- extend db methods for setting values to 'default' page
 flatdb.hack.set = function(db, key, value)
 	db.default[key] = value
 end
@@ -97,21 +97,21 @@ flatdb.hack.guard = function(db, f)
 	setmetatable(db.default, {__newindex = f})
 end
 
--- get key-value data from 'default' book
+-- get key-value data from 'default' page
 print(db:get("hello"))
 
--- set key-value data to 'default' book
+-- set key-value data to 'default' page
 db:set("hello", "world")
 
--- get key-value data from 'default' book
+-- get key-value data from 'default' page
 print(db:get("hello"))
 
 -- set guard function
-db:guard(function(book, key, value)
+db:guard(function(page, key, value)
 	print("CREATE KEY permission denied!")
 end)
 
--- try creating new key-value pair to 'default' book
+-- try creating new key-value pair to 'default' page
 db:set("key1", 1)
 db:set("key2", 2)
 
@@ -122,7 +122,7 @@ print(db:get("key1")) -- prints nil
 print(db:get("key2")) -- prints nil
 print(db:get("hello")) -- prints 'bye'
 
--- store 'default' book to './db/default' file
+-- store 'default' page to './db/default' file
 db:save()
 
 ```
@@ -136,15 +136,15 @@ API
 
       Bind a directory as a database, returns nil if 'dir' doesn't exists. Otherwise, it returns a 'db' obeject.
 
-  - **db:save([book])**
+  - **db:save([page])**
 
-      Save all books or the given book(if specified) contained in db to file. The 'book' argument is a string, the book's name.
+      Save all pages or the given page(if specified) contained in db to file. The 'page' argument is a string, the page's name.
 
 - **Tables**
 
   - **flatdb.hack**
 
-      The 'hack' table contains db's methods. There is only one method 'save(db, book)' in it by default.
+      The 'hack' table contains db's methods. There is only one method 'save(db, page)' in it by default.
       It is usually used to extend db methods.
 
 Dependencies
diff --git a/cli.lua b/cli.lua
index 008a7bb..cb6a596 100644
--- a/cli.lua
+++ b/cli.lua
@@ -22,7 +22,7 @@ local function split(s, sep, maxsplit, plain)
 end
 
 local db = assert(flatdb("./db"))
-local book = "0"
+local page = "0"
 
 local function handle(input)
 	local c = split(input, " ", 2)
@@ -41,59 +41,59 @@ local function handle(input)
 			end
 		end
 		if db[key] then
-			book = key
+			page = key
 			print("OK")
 		else
 			print("ERROR")
 		end
 	elseif cmd == "GET" then
-		print(pp.format(db[book][key]))
+		print(pp.format(db[page][key]))
 	elseif cmd == "SET" then
 		local ok, tmp = pcall(load("return "..tostring(value), "=(load)", "t", db))
-		db[book][key] = ok and tmp or value
+		db[page][key] = ok and tmp or value
 		print("OK")
 	elseif cmd == "INCR" then
-		if not db[book][key] then
-			db[book][key] = 0
+		if not db[page][key] then
+			db[page][key] = 0
 		end
-		db[book][key] = db[book][key] + 1
+		db[page][key] = db[page][key] + 1
 		print("OK")
 	elseif cmd == "DECR" then
-		if not db[book][key] then
-			db[book][key] = 0
+		if not db[page][key] then
+			db[page][key] = 0
 		end
-		db[book][key] = db[book][key] - 1
+		db[page][key] = db[page][key] - 1
 		print("OK")
 	elseif cmd == "RPUSH" then
-		if not db[book][key] then
-			db[book][key] = {}
+		if not db[page][key] then
+			db[page][key] = {}
 		end
-		table.insert(db[book][key], value)
-		print(#db[book][key])
+		table.insert(db[page][key], value)
+		print(#db[page][key])
 	elseif cmd == "LPUSH" then
-		if not db[book][key] then
-			db[book][key] = {}
+		if not db[page][key] then
+			db[page][key] = {}
 		end
-		table.insert(db[book][key], 1, value)
-		print(#db[book][key])
+		table.insert(db[page][key], 1, value)
+		print(#db[page][key])
 	elseif cmd == "RPOP" then
-		if not db[book][key] then
-			db[book][key] = {}
+		if not db[page][key] then
+			db[page][key] = {}
 		end
-		print(table.remove(db[book][key], value))
+		print(table.remove(db[page][key], value))
 	elseif cmd == "LPOP" then
-		if not db[book][key] then
-			db[book][key] = {}
+		if not db[page][key] then
+			db[page][key] = {}
 		end
-		print(table.remove(db[book][key], 1))
+		print(table.remove(db[page][key], 1))
 	elseif cmd == "LLEN" then
-		print(db[book][key] and #db[book][key] or 0)
+		print(db[page][key] and #db[page][key] or 0)
 	elseif cmd == "LINDEX" then
-		if db[book][key] then
+		if db[page][key] then
 			local i = tonumber(value)
-			if i < 0 then i = i + #db[book][key] end
+			if i < 0 then i = i + #db[page][key] end
 			i = i + 1
-			print(db[book][key][i])
+			print(db[page][key][i])
 		else
 			print("nil")
 		end
@@ -106,7 +106,7 @@ local function main()
 	end
 	io.stdout:setvbuf("no")
 	while true do
-		local prefix = book == "0" and "" or ("["..book.."]")
+		local prefix = page == "0" and "" or ("["..page.."]")
 		io.write("flatdb"..prefix.."> ")
 		local input = io.read("*l")
 		if string.upper(input) == "EXIT" or string.upper(input) == "QUIT" then
diff --git a/flatdb.lua b/flatdb.lua
index 12416aa..c85c8d6 100644
--- a/flatdb.lua
+++ b/flatdb.lua
@@ -9,16 +9,16 @@ local function isDir(path)
 	return lfs.attributes(path, "mode") == "directory"
 end
 
-local function load_book(path)
+local function load_page(path)
 	return dofile(path)
 end
 
-local function store_book(path, book)
-	if type(book) == "table" then
+local function store_page(path, page)
+	if type(page) == "table" then
 		local f = io.open(path, "wb")
 		if f then
 			f:write("return ")
-			f:write(pp.format(book))
+			f:write(pp.format(page))
 			f:close()
 			return true
 		end
@@ -29,16 +29,16 @@ end
 local pool = {}
 
 local db_funcs = {
-	save = function(db, bk)
-		if bk then
-			if type(bk) == "string" and type(db[bk]) == "table" then
-				return store_book(pool[db].."/"..bk, db[bk])
+	save = function(db, p)
+		if p then
+			if type(p) == "string" and type(db[p]) == "table" then
+				return store_page(pool[db].."/"..p, db[p])
 			else
 				return false
 			end
 		end
-		for bk, book in pairs(db) do
-			store_book(pool[db].."/"..bk, book)
+		for p, page in pairs(db) do
+			store_page(pool[db].."/"..p, page)
 		end
 		return true
 	end
@@ -48,7 +48,7 @@ local mt = {
 	__index = function(db, k)
 		if db_funcs[k] then return db_funcs[k] end
 		if isFile(pool[db].."/"..k) then
-			db[k] = load_book(pool[db].."/"..k)
+			db[k] = load_page(pool[db].."/"..k)
 		end
 		return rawget(db, k)
 	end