The first thing to know about the new George R.R. Martin book “Fire and Blood: 300 Years Before A Game of Thrones” (Bantam, $35) is that it’s not the George R.R. Martin book we all want.

That would be the ceaselessly delayed “The Winds of Winter,” the sixth novel in his world-conquering series “A Song of Ice and Fire,” which is the basis for the HBO hit “Game of Thrones.”

Instead, “Fire and Blood” offers a charming if intimidatingly dense pre-history to ASOIAF (as fans abbreviate “A Song of Ice and Fire”).

It concerns the rise and reign of the Targaryen family, toppled not long before the first of Martin’s books. You probably already know one of that family’s members: Daenerys Stormborn, queen-in-exile, the one with the dragons.

Here are five takeaways from this chronicle of her ancestors:

1. The parts that are good are…good!

For those with lingering doubts that “The Winds of Winter” will ever appear, “Fire and Blood” shows that Martin is still a powerfully gifted, inventive writer, albeit one bedeviled by an instinct toward overabundant world-building.

“Fire and Blood” is something between a short-story collection and an encyclopedia. It has hundreds of fascinating anecdotes, ranging from the cruel fate of a jester named Tom Turnip to a dragon that tellingly refuses to venture beyond the Wall.

2. But it’s not for new readers.

For a reader who isn’t acquainted with ASOIAF, it’s difficult to conceive of a worse introduction than this book. Within just his opening pages, Martin assumes the reader’s familiarity with dozens of points of geography, the basic character of places like Casterly Rock and Winterfell, the desert stubbornness of Dorne and much, much more. If you don’t know what it means to take the black, turn back.

3. You might see these characters on TV soon.

Part of the reason “The Winds of Winter” is so oft-deferred is that Martin and HBO could be developing as many as five prequel series based on ASOIAF. The one closest to screens is “The Long Night,” set to star Naomi Watts, which the network promises will reveal “the horrifying secrets of Westeros” and the “Starks of legend.” It’s hard not to think that further series could draw on the rich material of “Fire and Blood.”

4. The Internet thinks Martin is slipping Muppets into ASOIAF.

As a Reddit thread initially pointed out, “Fire and Blood” features a character named Kermit Tully, Lord of Riverrun, with a brother named Oscar who’s — wait for it! — grouchy. Characters in the same family tree have been named Grover and Elmo.

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