I havn't actually seen a book on detector comparisons, as such, but I have seen posts on this forum that compare the Quatro to other detectors and go into some specifics. I heartily agree with Golden that, whatever you buy, learn that darn unit. Learn everything about it, and it'll help you, but I'd go to some of the earlier posts about comparisons, or maybe to the other detector "types" even on this forum. I'd also just get on the "net" and start searching for info on that. Read what other detectorists with other types of detectors say about their detector. I did that, before I bought my Quatro, and that helped me make a decision on the Quatro. As for me, I'm happy as a clam, but everyone has they're own prefrences, so do your reaserch and that should help you. One last resource, and I hope I don't get in trouble for saying this, but: I called Kellyco and asked a "bunch" of questions before making a decision. I think they're expert people over there and they're probably one of the biggest most varried metal detector stores in the world. I'd say they have a lot to offer as far as info.