WOW! What a sourcebook!
The encounters here aren't simple adventure hooks, but rather fleshed out ideas that you can drop right into your campaign whenever needed. Clocking in at around a page each, the encounters outline environments, foes and their motivations, possible courses of action for the party, and outcomes that can lead to futher adventures. These might be short diversions for your group, or could easily be entire play sessions.
The three pillars of adventure are carefully attended to, with lots of opportunites for combat, exploration, and roleplay/interaction. Spanning all tiers of play, the location (eg onboard ship, at port, on island, etc) and focus (combat, social, exploration) are helpfully denoted with tables in the first chapter of the suppliment making it easy to find something that suits where your party is tonight.
Monsters from Volo's Guide and Mordenkainen's are utilized in many but not most of the adventures, so you'll want those resources to get the most value from this suppliment. Some might see this is a complaint; I consider it a compliment.
If published individually, these encounters could easily sell for a buck each. This book is an insane value at its low price. I really hope we can look forward to a print on demand version soon!