Lookingbill is something you're gonna want to reread towards the end of the year. Our first year derm residents currently are constantly worried that the med students on the service will show them up, because they've spent a year repleting potassium and managing heart failure, and forget what a dermatofibroma is.
If you're dead set on doing some heavier derm reading during your TY, like asmallchild said you could probably begin to familiarize yourself with one of the core texts (most programs seem to do some combo of Bolognia and Andrews, so that might be a place to start, but you could check with your future program too). Andrews, while much more condensed than Bolognia, tends to be (in my opinion) less than idea to start with, since it sometimes presupposes knowledge on your part, or at least whizzes right by some basic stuff you may not have down yet.
It would be painful as hell, but slogging through some of the more basic/rudimentary/basic sciencey chapters in Bolognia would at least make it less painful when you hit them for real at the beginning of your derm residency. But why taint what will likely be a reasonably good year as far as intern year goes?
FWIW, I did absolutely zero derm reading during intern year, entered derm residency feeling like an idiot, and I still managed to do very well on the in-service exam in February. In a way, it's like the premed dilemma of whether to "pre study" before medical school. Generally, it's not advisable and is a poor use of your time . . . but if you've made up your mind anyway, try to keep it simple/stick with basics to get a lay of the land.