I have Kaplan comlex books. They're basically the same as the usmle ones with a few comlex specific references here and there. I just started using them this month. I definitely recommend them. For me, they are good way to relearn the material before going through first aid
I have been using the books as another resource but as for board studying, they will become a reference if needed. We got access to Kaplan High Yield stuff online as well and I friend that is in 3rd year said that is exponentially more valuable to go through. So I don't plan on spending much time with the books.