Tomb of Annihilation is a great campaign in a wonderful setting, but the book can only cover so much content. Many areas of Chult can feel a bit empty because of this—ostensible landmarks may get just a paragraph of description in the hardcover, but it's characters and adventure hooks that make a place feel alive. Mr. Kahn breathes life into those Chultan locales that need it most.
These supplements are easy to implement on the go. When one of my players suddenly couldn't attend a session and I needed a sidequest to occupy the rest of the party, "Escape from Malar's Throat" made me look prepared. The author gave special care to emulate the descriptive style of Tomb of Annihilation, making the transition a seamless one. And just like in the module itself, it's very easy to utilize what you want from Mr. Kahn's adventures and leave the rest behind. The inspiration alone is well worth the price tag!
This series has made my life much easier, and I plan to incorporate as much of it into my campaign as possible. If you're a DM, do yourself a favor and take a look.