The UKCAT (United Kingdom Clinical Aptitude Test) is an admissions test required by most UK medical schools. They use the score from this test as a threshold, cumulative point system or a way to choose between very similar applications.
It is an aptitude test so it does not contain any curriculum or science content. (Does that make it easier or tougher? No idea )
Fact remains, we all still have to prepare for it. Many good candidates have been unsuccessful just because they had a weak UKCAT score. If you're going to apply to universities that require you to sit this exam, here are some links you should check out:
Whether you can't figure out which book to get or when to sit the exam, here's a thread to discuss it all!
All the best!
P.S. Here's a thread to discuss everything else related to applying this year: http://www.thestudentroom.co.uk/show....php?t=3962957