As a student that recently compleated a masters in forensic science, in which my thesis was an entomology based practical, i have read most books on the subject from the memoirs of Dr Zak and Dr Goff, to Bryd and Castner, Greenberg and Kunich as well and Smiths "mannual" and Catts "procedural guide", and i must say that this is the best starting point for an undergraduate, it has a few major points i must highlight,
first is avalible in a cheaper paper back which can keep the cost down (compare this with all the other forensic entomology books), Second this book has worked examples of the maths involoved, as well as questions to test yourself, also how to use excel to do some of the work. Thirdly it includes lab protocals, which a lecturer could use to form the basis of a practical, (also the amateur entomologist could use them for taxonomic studies), the book i feel is lucid enough for the beginer (a problem that can vex the higher priced texts), and yet authorative enough that the more advanced can still find new infomation in,
Of course if you are very serious about the subject you will own all the books, but this is where i would recomend to start
Andy