I use www.booking.com as one of four favorite travel search engines for the below benefits:

Low Prices

As the market leader in Europe, Booking.com offers you highly competitive hotel rates in both cities and regional destinations – ranging from small family hotels to luxury hotels.

No reservation fees

Booking.com's reservation service is free of charge and they do not charge you any booking fees, administration fees, or cancellation fees.

Secure booking

Their reservation system is secure and your credit card and personal information is encrypted. They work to high standards and guarantee your privacy.