No, it's legit. Booking.com is the only 3rd party website I'll use to book accommodations. They get the best prices and give you the option to book and cancel without penalty in most cases.

In fact, I booked one night thru the hotel directly and one thru Booking.com at the same hotel. The hotel overcharged me by trying to circumvent Booking.com. I prefer the guarantee of Booking.com and unless it's a reputable and international hotel chain, I won't go directly to the hotel on "trust" and "pay upon arrival". I was bait and switched on the night I did NOT go thru Booking.com - so Booking.com has earned my trust.

Further, when I had an issue, Booking.com genuinely tried to resolve it for me with customer service agents who didn't write canned responses - but took the time to read and understand the issue. I will definitely use Booking.com again.