These notes answer the questions a reader or team usually has before buying a book, bringing in a workshop, or asking Erik "Happi" Stenman to look at a difficult system.
The archive below keeps older notes without repeating the highlighted quotes.
Is The BEAM Book Useful?
The strongest feedback comes from engineers who needed to understand the BEAM at runtime depth.
"A must-read for any #erlang or #elixirlang developer."
"Recent discussion reminded me about this great book on lower-level working of ERTS/BEAM by @erik_stenman. Highly recommended; I'll reread it myself :-)"
"Have read the Beam Book - it helps to understand how BEAM VM works, and how to use it better."
Can Erik Help Senior Teams?
The relevant pattern is direct senior judgment during technical pressure: architecture, roadmap, hiring, and ownership.
"His background having lead and scaled technical teams at Klarna was a distinguishing factor... I would highly recommend Happi to any early stage founders and executives building in tech."
"Eventually, and also thanks to Erik's contribution, our company was acquired by a strategic buyer after only 18 months mainly due to our innovative technology."
Does This Work Survive Production?
Production feedback matters more than broad praise. These quotes connect the work to performance, risky systems, and high-volume platforms.
"If you are searching for a motivated team that will go the last mile with you, deliver qualitative stuff and understand bad jokes…Happihacking is the right choice!"
"HappiHacking provides solid engineering even in the most risky projects!"
"The information in this book has proven invaluable to better understand process scheduling, garbage collection and memory allocators and greatly improve the performance of RabbitMQ, both through more efficient algorithms and better VM configuration."
Is the Course Worth Bringing to a Team?
The BEAM course works best when a team wants a better shared model of processes, supervision, runtime behavior, and application design.
"I found the philosophical part useful for the team to design our applications."
Full Archive
Older community notes, reviews, and client quotes remain grouped by source.
Community Feedback
"A must-read for any #erlang or #elixirlang developer."
"Recent discussion reminded me about this great book on lower‑level working of ERTS/BEAM by @erik_stenman. Highly recommended; I'll reread it myself :-)"
""I kept going because I wanted to understand the BEAM properly." There's value in following the real logic, not just the surface explanations."
"The BEAM really feels like alien tech left from a highly advanced civilization and this book dropped in at such a great timing! Bought it right away, kudos to Dr. Erik Stenman for keeping it up after two cancellations!"
"Bought it instantly, even if it's available online for free—I guess this way supports the author a little bit."
"Plenty of documentation can be found about the JVM, but BEAM has always seemed like a bit of a mystery to me. This is great!"
"Books ask for a lot of organization in general. And books on an evolving subject never stop asking. I don't use Erlang, but for 13 years in the making, I'm getting a copy. Thank you."
"Thank you for writing this book! I really wanted this a few years ago as I was debugging production Elixir, when existing learning sources were pretty dense and dry (or too simple and shallow)."
"I found the philosophical part useful for the team to design our applications."
"Continue being awesome."
"Recent discussion reminded me about this great book on lower-level working of ERTS/BEAM by @erik_stenman. Highly recommended, I think I'll reread it myself :-) blog.stenmans.org/theBeamBook"
Client Feedback
"Tobias is one of the more talented Engineers I have had the pleasure to work with... I can highly recommend Tobias and there will always be an open position in my organization for him."
"Impressive! This firm dug into our tech and got started fast! Their work was excellent and more importantly, diligent! They stood behind their work and took ownership! I give them 5 stars for sure!!!"
LinkedIn Endorsements
"theBeamBook from github was one of my first references when I learned Erlang for a corporate project … it never disappointed me and clearly expressed concepts and powerful features of BEAM and the language itself. I'm glad you've been awarded with results you totally deserve."
"It is [a] bargain for just USD 25 plus shipping to Sweden! I had the pleasure to browse a physical copy at last BEAM LITE in Stockholm. Congratulations to Erik and us readers!"
"Any programmer should learn at least three mind‑opening languages … any BEAM language to see how to build fault‑tolerant and distributed systems. I look forward to reading this book."
"Just bought my copy in this very moment! Long live the BEAM!"
"I've bought my copy right after seeing the paper version. What a huge work. Thank you so much!"
"When I saw it I thought of the movie Hackers and how they name books by colour … This would be 'the red book.' I purchased a copy, of course."
Amazon Reviews
"Essential for anyone who needs to tune performance or understand how Erlang / Elixir really run."
"Packed with insights … a quintessential read for every BEAM developer."
"An epic contribution from 'Happi'—finally explains what happens after you hit Save."
X and Twitter Notes
"The BEAM Book is now published on GitHub! Thank you @erik_stenman 😊"
"Really enjoying the BEAM Book..."
"Referencing @erik_stenman's BEAM expertise"
"Probably the Beam Book is one of the best resources that every elixir develop should read to understand the BEAM vm."
"I believe there are at least two resources that are a must for Elixir developers: the first one is Joe Armstrong's thesis, and the second one is the BEAM book."
Verifiable Achievements
The BEAM Book Recognition
- 5.0/5.0 ⭐ Rating from verified buyers on Amazon
- #1 New Release on Amazon (US & Sweden)
- Featured #1 on Hacker News with hundreds of comments
- More than 3800 stars on GitHub
- GitHub Sponsors including Jose Valim (Creator of Elixir)
Academic Credentials
- PhD Thesis: "Efficient Implementation of Concurrent Programming Languages" (Uppsala University, 2002)
- Advisor: Kostis Sagonas
- Opponent: Simon Peyton Jones (Microsoft Research)
Open Source Contributions
- Kappa Framework: Originally developed at Klarna, now open source
- Erlang/OTP: Contributions during HiPE research and Klarna scaling
- æternity: Core team member and primary designer of FATE
Contact for Endorsements
If you have read the work, used a tool, taken a course, or worked with Erik and want to provide an endorsement, send a note to info@happihacking.com.
