I've read the authors' presentations and thinking behind the program's design and I was impressed, but I think the end product they came up with just lacks anything special to recommend it. It's dry, slow, and not particularly fun.
I haven't done SICP so I don't know what a good prereq would be, but I remember The Little Schemer being entertaining and covering the same sort of ground as HTDP at a better pace.
I didn't quit after one chapter. I explained my experience in hopes of saving someone else from wasting time.
Edit: I didn't downvote you.
Other potential prerequisites to SICP, all of which use Scheme: The Little Schemer (http://www.ccs.neu.edu/home/matthias/BTLS/; a quick read, but a bit overly cute), EoPL (http://www.cs.indiana.edu/eip/eopl.html; a great book in its own right; I recommend the _first_ edition), PLAI (http://www.cs.brown.edu/~sk/Publications/Books/ProgLangs/).
Good story about it here: http://www.trollope.org/scheme.html
It was cut from later editions, for some reason. Too advanced? Too tangential to the rest of the book? Too bad.
The first edition is also really cheap. FWIW.
I've also used Picturing Programs (http://picturingprograms.com/philosophy.html) and "How to Design Worlds" (http://world.cs.brown.edu/) with a few students that had a great deal of math anxiety and wanted a more graphics-intensive approach. I myself had/have a great deal of math anxiety, so I appreciate all of their efforts on this front. All of these materials help student's get their feet wet before they get too scared of the waves.
BTW, Does anyone know if someone has worked out the kinks so that you can use SICP examples directly in DrScheme/Racket to make the transition from HTDP to SICP easier for students? The last time I tried it, there were too many little gotchas and I gave up due to (volunteer work) time constraints.
http://www.neilvandyke.org/sicp-plt/
Hope it helps.