I haven't used them for step 1 (still an MSII) but I have used several of the recall books for class work (path and pharm) and they seem fairly effective. Their main value is for practicing active recall of material (hence their titles) instead of passive reading.
The Secrets series is pretty similar to the Recall series w/ a Q and A format except their explanations are longer and more complete. Average explanation for Recall is 2 or 3 words per question, maybe a line of text at most. Average explanation for secrets is usually 2 or 3 lines of text, often a complete paragraph. Next time you hit up the book store, compare Pathology Recall to Pathology Secrets, and you'll know exactly what I'm talking about.
