Avantages
Nice people, pleasant atmosphere, nice office, good lunch, great work-life-balance, good salary (compared to most other Dutch companies).
Inconvénients
For back-end developers Booking.com has absolutely nothing to offer. The quality of code is just horrific and building on top of the house of cards is the norm. OO? Tests? TDD? DDD? Any design at all? Forget about it. 2000 line Perl functions with 1000 line if-else-statements are perfectly normal and not even frowned upon, even by principal engineers. Perl is still the language you will work in (despite what they say in interviews) and Perl is simply unfit for building quality back-end systems. There are a few teams doing cool stuff, but you have to wait 8-20 (!) months before you can pick a team you like. Run away from this company if you want to learn anything useful as a back-end developer. You'll be a worse programmer when you come out compared to when you came in. Do join though if you want to go back 15 years in time.