I'm about to go to uni and want to develop a more professional understanding of electronics as I'm a hobbyist at the moment. Obviously there is a lot of information online, but it always seems rather incomplete. There also seem to be a lot of books around, but there is always the problem of choice. The book that I have read a lot of good reviews about is "The Art of Electronics" by Paul Horowitz and Winfield Hill. Now to my question, what books and other references do you use and what are the essentials that everybody should have read to gain a more in depth understanding.