|Being a long time Perma DM, I was really looking forward to this book bundle. After purchasing the bundle of all these monster loot books on sale I was very hopefully, but when I read through them I was honestly a little underwhelmed but still did enjoy what I got. First the Negative.
A decent amount of the Monster Manual loot of the book I will say first and foremost feels like filler. A prime example of this is the section on Mephits. Each type of Mephit (Fire, Mud, Steam, etc) are listed, and each one gives the EXACT same loot, with full description of what the loot in question does. That is five excess entries that in my opinion are filler. The book does not want to encourage the dreaded murder-hoboing of humanoids so does not give them harvestable loot for the most part (Understandable), but still goes out of its way to list "Broken (Equipment)" on every humanoid entry, which feels highly pointless for this type of book and no more than filler with how many times this loot is the only thing listed for such entries (I did come across a couple with something actually harvestable listed, I will get to that in a moment.). Also pricing for craftables of these materials I find render harvesting of mundane goods pointless quite a few tunes (To make plate armor out of X it costs the full price of plate armor that does nothing but act like plate armor). I also feel many of the monster entries are a bit underwhelming. You kill an Ancient Dragon, and apparently dragon hearts, eyes, and many more organs have no cost or function associated with them for Ancient Dragons, they are not even listed in the dragon's entry.
Now that the negative is out of the way, onto the positive.
Where this book shines best is in its interesting/creative loot. Kraken parts for example have many uses, and create some unique and fun items as well. The humanoids that do have loot are interesting enough to stoke the fires of the imagination, and having solid lists of parts for every non-humanoid creature is very useful. While I was a little underwhelmed, do not take that as disappointed, just not as fulfilled is all. I do not feel like I wasted money on these books/pdfs in the least. In fact, I still use these books as launching points when my players ask questions on loot and then make up the rest from there. These books can really help take a huge stress out of DMing. "I want to harvest the dragon, what do I get?" now has an answer just waiting for you, and nothing says you cannot tweak or make up your own results based on what this book gives you.
TL;DR: A fine book, I just wish it went further. A lack of lore filled/marketable harvestables (While not magic, surely dragon eyes, hearts, etc must hold some value) holds this back from being a perfect book, but for what you pay you're provided a strong starting point to write your own tables if you so desire or just use as is.
[4 of 5 Stars!]