Not to Google Standards
I have been traveling overseas and I have had a ton of difficulties with this app.
First of all when you get a blue checkmark as the book is synced, it isnt so. And if you go outside of internet range your book will disappear.
The work around is to go where internet is available, go to the first page of the book and scroll "manually" page by page up to the end of the book so it syncs all pages.
Only in that scenario, the book can be seen offline.
Also if you have issues consider deleting the book, closing the app (double tap home key, and scroll background app to close) and then do the steps above.
houmi about
Google Play Books - Books & Comics