Good Times! is a picture book tie-in adaptation of the second half of the Spongebob Squarepants episode/special, Truth or Square. Specifically, it deals with the plotline of the "Krusty Krab's eleventy-seventh anniversary" (which, of course, begs the question of exactly how old Mr. Krabs is supposed to be...) and Spongebob's recounting his favorite Krusty Krab-related memories. However, it removes the framing device of the episode--that SpongeBob, Patrick, Squidward, and Mr. Krabs have gotten trapped in a freezer--and also manages to take out all of the humor.
Thus the story is left as a random sampling of very short Krusty Krab anecdotes interspersed throughout Spongebob's present-day narrative. The book cycles between past and present without much fanfare, which I imagine might leave some younger readers a bit befuddled; the flashbacks are given a daydream-esque sparkly border to make them stand out more, but I still found the immediate transition to be a tad... inadvisable, perhaps.
Again, I don't really see the point of the book. If your kid is a fan of the show, they'll likely be disappointed by the lack of humor in this adaptation; at best, it'll remind them of the episode's funny moments and garner a laugh that way. The only reason I can really see to advocate this book for any child's reading schedule is the case of reluctant readers who also happen to be Spongebob Squarepants uberfans; perhaps they'll see some appeal that I don't.