non LL(1) grammar but LL(1) language
Well a language is XX iff there exists an XX grammar for it. There might be other grammars for an XX language. For instance you might have a context-free grammar for what is actually a regular language.

Read the book. It contains techniques (with examples!) that show how some non-LL(1) grammars can be transformed into LL(1) grammars. The techniques are called elimination of left recursion and factorization.