The Scheme Programming Language by R. Kent Dybvig is very much worth reading after you finish SICP. Truly the same caliber as K&R's C Programming Language, and more up-to-date (R6RS). The earlier exercises aren't too tricky (except call/cc headaches), but the final chapter has some good meaty Scheme projects that will teach you a ton.

It's free online: https://scheme.com/tspl4/