The book got all wet and the pages were wrinkly because the baby was sucking on it.
The baby kept putting the book in his mouth so the pages got all soft from his saliva.
1) The book got all wet and the pages were wrinkly because the baby was sucking on it.
「赤ちゃんがなめていたので、本が濡れてページがシワシワになった。」
この場合の「濡れてふやける」は wet and wrinkly を使って言うと良いと思います。
the book got wet and the pages were wrinkly で「本が濡れてページがふやけた」
2) The baby kept putting the book in his mouth so the pages got all soft from his saliva.
「赤ちゃんが口に本を入れるから、ページが唾液でふやけた。」
ここでは get soft from one's saliva で「ふやける」を表現しました。
saliva で「唾液・つば」
ご参考になれば幸いです！
日本 
