As the link in samth's comment describes, they are really different books that had different goals. If I remember correctly, HtDP was partly inspired by the big

As the link in samth's comment describes, they are really different books that had different goals. If I remember correctly, HtDP was partly inspired by the big chunk of SICP that requires somewhat external domain knowledge (mostly calculus and some electrical engineering), and the authors wanted to write an intro CS book that didn't require any special prerequisites. They were also written in different times, for different audiences. Didn't MIT combine their CS and EE curriculums as "course 6" (and still do?) requiring someone who was ostensibly majoring in CS to do a lot of EE, physics, and calc? I imagine CS was a different kind of major in the 80s when SICP was first written than it was when HtDP was first conceived. I tried to read it, after having read SICP, but I couldn't get past two or three chapters. It's very much geared toward a complete beginner to programming and goes quite slowly, with tons of hand holding examples. This isn't really a fault, they obviously cannot satisfy a complete beginner and a working programmer with a CS degree who wants to fill in holes in their knowledge. I'd like to try to go at it again, maybe after they finish updating it, perhaps doing what Norman Ramsey has said on Stack Overflow in recommendations of the book: "If it's too easy, go faster!". There's a review on Amazon from someone who claims to have a PhD in CS, who said it was very valuable. (maybe that says something about their PhD program? zing! I jest.) So take my review with a dose of salt.