Does reading a c++ 11 book requires to have knowledge of c++98?

C++11 is not a separate language. It's just a new version of the existing one. Reading a C++11 book requires whatever prior knowledge that the C++11 book says it requires.

Bjarne's new version of "The C++ Programming Language" expects no prior knowledge of anything. Some other books will expect prior knowledge.

Actually, given the changes from C++98 to C++11, I'd recommend not reading an old book beforehand.

This is because a lot of old methods and idioms have been replaces with much neater constructs and features, which avoid many pitfalls and issues that C++ programmers had to contend with earlier. A coarse comparison would be to read up on relays and electron/vacuum tubes in order to, eventually, understand how to build transistor based logic. No need to start at that end.

So, I recommend you want to read on what's current, then it wouldn't hurt to read an older book to understand why a lot of already existing C++ code was written like it was.

If it's an "what's new in C++11", then you obviously need to know C++98 beforehand.

But as @Nicol says, the book should declare what previous requirements it has.