After finding this excellent
podcast, I've read two recommended books on democratic reform in the United States:
Breaking the Two-Party Doom Loop: The Case for Multiparty Democracy in America by Lee Drutman.
Let the People Rule: How Direct Democracy Can Meet the Populist Challenge by John G. Matsusaka.
Both are ambitious enough to be interesting (unlike low hanging fruit such as abolishing the electoral college) and at the same time realistic in the sense that they are based on existing institutions in the US and abroad. The first book focuses more on history and the latter more on scientific evidence. Both are very US-centric, which I think is a problem for the first book, since the US has little recent experience with multi-party democracy.
I pretty much agree with the reform proposals of the first book (namely multi-member districts with ranked-choice voting). The second book however recommends to start with advisory referendums (i.e. referendums initiated by the legislative majority) because bottom-up binding referendums would require a constitutional amendment. That seems like a bad idea to me. Advisory referendums can be problematic by themselves, but could be especially bad within the US system in the current political climate.
In any case, I'd rate them 3 out of 5 stars. As long as you don't expect great literature I can recommend both.