This is a hefty and cheap addition to the D&D supply of rituals. There's a large array of rituals, some obviously more likely to be useful than others. They seem ideal for a DM to introduce as researchable rituals, perhaps as solutions to a specific problem, or as rare treasures appropriate to the adventure. As well as using the rituals as given, the large array here could be templates for similar rituals created to fit your campaign. Although I haven't yet used any of them in my campaign, I'm already prepared to say it's worth the price.
However, there are a couple of drawbacks to this product, which won't bother everyone.
The first is that the book is presented by hobgoblin general Azagar, which means fairly salty language and anecdotes at the head of each chapter. If you're sensitive about these things, or are running a game for children, you might need to censor it a bit. The rituals themselves are not affected by this, and as businesslike as any other rulebook. I didn't mark the product down for this, as it doesn't bother me and it's a very subjective point.
Secondly, I'm sorry to say there are a significant number of typos, spelling and grammatical errors, and other minor editing slips. I find these jarring, though not everyone will care. In a couple of cases, the exact effects of a ritual are unclear because of ambiguous language, which is a bigger problem. Given the size of the product, it's not too bad, but I still knocked off a point for this because it's affected the quality.
If there's a follow-up product, I would love to see a range of cheap everyday rituals. Rituals that would be useful and affordable for ordinary farmers, artisans, tradespeople etc. would be a very interesting addition from a world-building and roleplaying point of view. However, I've certainly no complaint about not finding them in here.
[4 of 5 Stars!]