The Artful Dickens
I just finished The Artful Dickens: Tricks and Ploys of the Great Novelist (2021) by John Mullan. Fantastic!

I just spent the last two years reading all of Dickens's main novels in chronological order. This was an online book club called the Mega Dickens Readalong. It was great fun!
Mullan's book is a perfect follow-up to this readalong! He talks about multiple characters and multiple books at once and it just would not be the same had I not just read them all. Also, it's filled with spoilers, so you might not want to read it if you plan on reading one or more Dickens novels that you haven't read yet.
Mullan is the author of What Matters in Jane Austen? Twenty Crucial Puzzles Solved (2012), which I also loved. The Artful Dickens is similar in that each chapter has a point to make and he draws from any of the books he chooses for characters or examples to support that point. Indeed, he even goes outside Dickens to other Victorian authors sometimes. It's just wonderful!