This book was exactly what I was looking for - a clear, detailed, comprehensive and up-to-date first aid book that is also pocket sized. Book contains suggestions for different levels of first aid kits, basics of first aid and a large list of both common and more rare diseases, their symptons and their treatments. Details of which antibiotics are useful when are particularly useful when travelling!
As other people have mentioned, some basic understanding of first aid or medicine is helpful to fully understand some of the diagnoses, and indeed to properly administer some of the treatments. However, this only makes the book applicable to not only those with basic first aid knowledge, but also those with more advanced training (even if it's just to serve as a reminder to their knowledge). In short, it is applicable to all and an excellent buy.