Fitzpatrick's Dermatology in General Medicine is the classic dermatology textbook1,2—so the question of whether a skin care professional needs to own it is moot. The real question is whether to buy the new seventh edition or scrape by with the 6th edition for a few more years.
Dunnick CA, Dellavalle RP. Fitzpatrick’s Dermatology in General Medicine. JAMA. 2008;299(10):1195-1196. doi:10.1001/jama.299.10.1195-b