Three-and-three-quarter stars, rounded up. There's a lot to like about this book, but there is also some places where it is somewhat problematic.
Part I, Fundamentals of Apache Iceberg, is well written and informative, although sometimes sounding a bit like marketing materiel ("Reading data from Apache Iceberg tables follows a well-defined sequence of actions, seamlessly allowing queries to be transformed into actionable insights."). It was my favorite part of the book, delving down into the file level and building up to Iceberg's architecture.
Part II, Hands-on with Apache Iceberg, on the other hand, had a bunch of very similar chapters with the same material covered with different query engines. If you were looking to understand how Iceberg worked and was used, this redundancy wasn't all that useful. Admittedly, if you just wanted to look up how to use one particular query engine with Iceberg, this approach is probably what you want.
Part III, Apache Iceberg in Practice, was OK, discussing Iceberg metadata, streaming, security and governance, migration and some meh use-cases, but was missing something important: a discussion of when and when not you should use Iceberg. This is large scale software for huge amounts of data. You really don't want to adopt it too early -- most companies will probably never have enough data to need Iceberg (but those that do, will really need it or something like it).
The authors all work for Dremio, but they do seem to be making an effort to be even-handled and cover all of the Apache Iceberg ecosystem. But they do seem to be a bit too used to selling, and I found some of it a bit off-putting (like describing the book in the introduction as "meticulously crafted"). There's a reason why most technical writing strives for a more neutral tone; many technical readers are put off by that sort of thing.
But despite these nits, it was definitely worth reading.