This came out at the end of my career as a serious professional cook and I have mixed experience with it. It's kind of an escoffier guide culinaire type deal for the 2000s. It documents & standardizes, or at least presents emerging conventions for, a huge range of techniques that were in use in certain kinds of restaurants in the preceding two decades.

In terms of food like that you sit down and eat with other people, it was narrowly focused and dated almost immediately. But some of the techniques and "moves" became genuinely mainstream and it's fairly reliable as a reference to them. And some of the others didn't, but could have and are useful, and unless you were cooking at one of a couple dozen restaurants from 2002-2008 you're unlikely to find another detailed guide to how to do them.

That said, for a lot of the detailed technical stuff, they generally chose to authoritatively select one specific approach to a technique, eliding details that can definitely be a big deal at this level of precision. Sometimes the "recipe" is really more of a demo, silently depending on details like a neutral pH, making it prone to failure if modified but too basic to be usable in its presented state.

Also some of the techniques simply don't work as written. Specifically the ones that are presented as novel simplifications for complex molecular gastronomy operations are really hit or miss. I suspect these are just really bad cases of the previous point, where there is a hidden variable they didn't document, that didn't come up in testing. But there is a replication crisis in cookbooks too, this is not out of the norm though it is frustrating.

It also raises the annoying question that's been in my head for 15 years now: wtf does myhrvold think "modernist" means?