Keep reading. ;) Seriously, if you're only 200 pages in, you haven't read chapter 3 yet, which delves deeply into the implications of introducing mutable state

Keep reading. ;) Seriously, if you're only 200 pages in, you haven't read chapter 3 yet, which delves deeply into the implications of introducing mutable state, and spends quite a lot of time exploring those implications, especially for concurrent programs. There is also some exploration into object oriented programming and alternative semantics and paradigms, including logic programming and laziness (chapter 4, iirc) In short, I definitely don't think of SICP as an absolute reference to functional programming, especially since there are newer languages and approaches to these problems (STM in Clojure and Haskell, actor based concurrency etc) but SICP is an absolutely brilliant introduction, albeit a long one.