Shannnon's start with this was his MS thesis in the 1930s, but of course he could have been exposted to phone switching before he was at Bell Labs.
Actually, there's tons of stuff about sequential circuits in KR&W, of which I have multiple copies, including Keister's personal copy signed by the authors. I helped empty his house when he moved to Cape Cod and he gave it to me -- and the Ritchie was my father.
The book was published in 1951, and the thing it doesn't have much about is transistor (let alone integrated) circuits. About as much space (a few pages) is on cold-cathode tubes.
Dennis