Before I ever buy a book, I check out a few pages inside the book to see how easy it is to read.
I always have a quick glance at any book before I decide to buy it.
この場合、次のような言い方ができますよ。
ーBefore I ever buy a book, I check out a few pages inside the book to see how easy it is to read.
「本を買う前は、どれだけ読みやすいか、中身を数ページ確認します」
to see how easy it is to read で「どれだけ読みやすいかを見る」
ーI always have a quick glance at any book before I decide to buy it.
「本を買うか決める前に、いつもさっと目を通します」
to have a quick glance at ... で「…にさっと目を通す」
ご参考まで！
カナダ 
