War Captain's Companion expands on the ship combat for 2d edition Spelljammer provided within the original boxed set. It has more detailed combat rules, descritpions of all kinds of spaceships, their equipment, way to maintain, obtain and fix them, etc. The main portion of the publication is ship descriptions and combat rules though - this one's made for this specific purpose, and for advanced space combat, it is pretty useful and well written.

Now, for the product available here: originally this one came in a box, but here it's either a PDF or all the contents packed into a singe, laser-printed print-on-demand book. Neither's perfect. Obviously the hexagonal playmat, the paper-mini-ships and combat counters are copletely unusable in the Print-on-demand format. The ship size comparison poster is on the verge of being of any use and even the player aid cards are just pages in the book, so their use becomes limited. Furthermore, the print itself is slightly blurry, it has a little blue haze, it's not as clear as for example the Spacefarer's Handbook's POD version. For these reasons, I also bought the PDF version, but the image quality is uneven. It has the same slight blur in places and the minis look okay at best. In the end I had to ask personal scans from someone else and then I had to manually retouch these scans to make some super-sharp minis. I couldn't work with the ones provided here.

All in all, the information in this one is useful, definitely cranks up the space combat to a more engaging level (but you can just use the rules found in the original spelljammer box-set as well), that said, the quality should definitely be better than this. PS: the book arrived very slightly damaged as well.