Interpreting ECGs is difficult, at least at the start, for most medical students. This book doesn't quite make ECGs easy but it does help to provide a reasonable introduction into how to begin understanding what the little lines and squiggles mean.
It starts off with basic info on the rate, rhythm and axis of ECGs then has a chapter on each of the main arrhythmias you'll come across. Some of the very basics in chapter one are not described very well (in particular, the cardiac axis paragraphs), occasionally lacking clarity and depth but they do use plenty of pictures to demonstrate what they are explaining to you and after a couple of reads you will begin to see what they are getting at.
Others have commented that the book could do with some more clinical details but I disagree - you should have a medical text book containing a section on cardiology already. I see it as a bonus that this pocket-sized book limits itself to the difficult enough topic of interpreting ECGs.
Lastly, there are 10 practice ECGs at the end for you to test yourseslf on, with answers explained fully.
Overall, I found it to be a useful book that can give you a reasonable introduction as to how to start reading, interpreting and presenting ECGs to your colleagues. It was great for last minute cramming before OSCE-type exams (at GKT anyway!), and should be good for anyone who doesn't have a kindly cardiologist who wants to teach you how to read them him/herself!