To get to the point, this DoubleJump guide is loaded with errors that shouldn't be there. Most of them are minor annoyances, but some leave out or misreport critical information. For instance, the Persona skills listed for Teddie are 100% inaccurate and are obviously meant for Kanji. Even worse, some enemy data is just plain wrong. I was fighting a rare monster called Luxury Hand once, the guide says Light skills are effective, so I cast Hamaon. Guess what? Blocked. The mistakes aren't just confined to tables. In one paragraph, the guide claims that in Triangle Fusions, if two personas are at the same level, the one with the higher arcana takes precedence. This is blatantly wrong, as it's actually the persona with the *lower* arcana that takes precedence.
While the more minor errors such as typos aren't as important, they're far more numerous and certainly aren't irrelevant. I'd honestly bet that more than half of the pages have one or more typos, doubled paragraphs, etc. Quite a nuisance.
However, despite all my complaints, I don't really regret buying the guide. It's extremely useful as a reference when you simply want to know an enemy's weakness, how to complete a quest, how to open certain doors in dungeons, how to respond in S. Link events, and a lot more. It's a whole lot more convenient to simply have a small book at your side rather than digging online for the info. And hey, it looks pretty snazzy, too.
In the end, I recommend a purchase only if you love Persona 4 and plan on spending many, many hours with the game, as I do, or if you simply enjoy using strategy guides. It's at least better than the typical slop Brady and Prima throw out, after all. Just be aware of the errors.