If you are a DM, you will want this book because it has a lot of things that would be helpful to your should your table wish to use it. Players will want this book for structure and ideas.
The Class background-like options and This is Your Life are both helpful for players that need structure to make backstories. Racial Feats can also be completely optional. The descriptions about tools and their possible uses helps DMs that need structure to what tools may or may not be able to do and what the conditions for success would be.
There's also some clarifications of existing rules in text - these are not Errata, but clarifications.
An entire section on building encounters is included - this will be very helpful to DMs. There's also an entire section on designing traps in a structured way, structure for buying and selling magical items, and a section of additional spells.
You can easily survive and run your table without this book, but it's a very helpful and useful one. While I've seen what books like this might do to Shadowrun, WOTC have produced a book that doesn't find itself "patching the game" like a Catalyst book usually does.
My personal advice is - due to the nature of additional class archetypes and other such things - I'd rule that this book qualifies for the "+1 book" rule in Adventurer's League fashion. If your players use this book, it should count as their "+1 book".