Mr. Penumbra’s 24-Hour Bookstore by Robin Sloan ★★★★☆ #BookReview #BookBlog


Primary Genre(s): Fiction, Mystery, Fantasy
Originally Published: 2 October 2012 by Farrar, Straus and Giroux
Page count: 288
My Format: Audiobook via Hoopla Digital
Cover: Bright (glows in the dark)
Pacing: Good
Ending: Okay
Would I recommend it: Yes
Commission Link:

My rating: ★★★☆

Summary from Goodreads
The Great Recession has shuffled Clay Jannon away from life as a San Francisco web-design drone and into the aisles of Mr. Penumbra’s 24-Hour Bookstore, but after a few days on the job, Clay discovers that the store is more curious than either its name or its gnomic owner might suggest. The customers are few, and they never seem to buy anything; instead, they “check out” large, obscure volumes from strange corners of the store. Suspicious, Clay engineers an analysis of the clientele’s behavior, seeking help from his variously talented friends, but when they bring their findings to Mr. Penumbra, they discover the bookstore’s secrets extend far beyond its walls.

My Thoughts
A few days ago I reviewed Sourdough by the same author and noted that I read Penumbra in 2016 but didn’t remember much about it (although I’ve read at least 500 books since then so it is at least a little understandable that I wouldn’t remember). I liked Sourdough so much that I decided to revisit Penumbra and I put it on my TBR list – which is a great honor, I must say, because I very rarely reread books. Well, Penumbra jumped to the top of the TBR… my curiosity got the best of me. I just finished it! Here are my pros and cons:


  1. Like Sourdough, Penumbra is quite a crazy ride! It is a story about secret codes in old books, code breakers, coding nerds, wizards, rogues, warriors, and fonts. It is such a mish-mash of weirdness that it absolutely works!
  2. I loved the juxtaposition of modern code breaking/puzzle solving (Google/computers) with the “old” way. I don’t know how much of the Google stuff was accurate, but I am presuming it was at least close. I have to admit that I am a little old school though – if you are solving puzzles and code breaking for fun, having the computer do it for you seems to take all the fun out of it. I guess if life or death is on the line, then bring on the computers!
  3. I think the author creates relatable characters. Interestingly, I found that the author wrote a short story (65 pages) called Ajax Penumbra 1969. I haven’t read it yet, but I am hoping it gives Penumbra a little more backstory. We get clues about Penumbra’s past in this book, but not details. I think that vagueness made him a more intriguing character overall, though.
  4. This book cover glows in the dark! According to Wikipedia, the cover was done by Rodrigo Corral and was chosen as one of the 25 best book covers for 2012 by BookPage.
  5. I liked the backstory of Clay and Neel’s friendship.
  6. I loved Kat. I always enjoy reading about smart, motivated women!


  1. There were a few “oh that is convenient” moments for me. I never like those, but I understand they are necessary sometimes to keep a story moving in the right direction – particularly a crazy ride like this one.
  2. I felt the ending was a bit of a letdown. I wanted to know what the ultimate “message” was, but the result was kind of disappointing. Not horrible, but more meh.

I felt myself reminded of Ready Player One by Ernest Cline a bit (which was published slightly before Penumbra) when I was re-reading this book. It was the “feel” of the book that made me compare the two. Penumbra is this crazy story that essentially involves a game of sorts where members of a (secret) organization find clues, break codes, solve puzzles, and use their resources and brains in order to complete the quest, so to speak. Ready Player One also put players on a quest to solve riddles and games in order to win the ultimate prize. The stories aren’t identical, but the feel of the books are very similar. If you liked Ready Player One, I think you’d also enjoy Penumbra.

I loved Sourdough (a story about foodies and a sourdough starter) and I loved Penumbra (a story about book lovers, puzzles and a quest). If the author writes his next crazy book about animal lovers, particularly cats, I will be a lifelong fan!! HA!

If you would like to read this book and form your own opinion, please consider purchasing through this link: As an Amazon Associate I earn from qualifying purchases at no extra cost to you. Thanks!

17 thoughts on “Mr. Penumbra’s 24-Hour Bookstore by Robin Sloan ★★★★☆ #BookReview #BookBlog

  1. I just started listening to Sourdough today and am enjoying it. I spent over an hour browsing my awesome Nashville Public Library’s collection of available eaudiobooks, and that’s the one that most caught my eye. I wanted to listen to Penumbra first since it was Sloan’s 1st novel, but my library only has the book, not the audiobook. It’s definitely going on my TBR, though!

    Liked by 1 person

  2. This is on my TBR pile. After reading your review, I may have to bump it to the top after I finish reading for book reviews and book launches! (Also, I loved Ready Player One.)

    Liked by 1 person

  3. I didn’t like this one at all due to the Google-latry. I can understand applauding Google’s value for internet research (even though there was at least one research job where Google wasn’t the best option) but when we wander into the awesomeness of Google’s cafeteria and the incredible efficiency of Google project manager meetings — the product placement killed it.


  4. Sourdough is weird and awesome! Ending is a tad meh, but didn’t ruin the book for me. If someone can write a book about a sourdough starter that keeps me engaged, then that is talent! I hope you enjoy it as much as I did.

    Liked by 1 person

  5. I think you will like it. Sloan’s books are very quirky and can be quite odd at times, but for some reason I just love them. Sometimes it is just fun to go off on a quest sometimes, right?


  6. I couldn’t remember it either, which is why I re-read it after Sourdough (his other book). I think I enjoyed it more in the second reading. The ending is a bit meh, but didn’t ruin the book. It is a fun adventure.


  7. The book definitely does do what you say… there is absolutely some Google worship going on for sure. Ultimately though, Google and all the Google coders couldn’t solve the puzzle. Perhaps that was ultimately a way to knock the behemoth off its pedestal a bit? Food for thought. 🙂


  8. Booklovers, puzzles and a quest? I need to read this. Somehow this novel slipped past me, so thanks for the review. I’ll be picking it up sometime in the next few months.

    Liked by 1 person

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