There is a book, sold by Amazon, "GMAT Test Questions (collection of 925 hard math questions from GMAT Club) [Kindle Edition]".
Is it the same as (paid) GMAT Club Math tests (1-25)?
The number of promised questions slightly different, so I am guessing there is an overlap, and if there is, what's the extend of it?
It is the same but the Kindle version does not have the Verbal questions offered online.
Also, Kindle sometimes screws up formatting, so I recommend the online version if you have a choice.
Founder of GMAT Club
Just starting out with GMAT? Start here... | Want to know your GMAT Score? Try GMAT Score Estimator
Need GMAT Book Recommendations? Best GMAT Books
Co-author of the GMAT Club tests
Have a blog? Feature it on GMAT Club!
Get the best GMAT Prep Resources with GMAT Club Premium Membership