This is really rather fun to play with: and worth considering whatever star-faring SF game you play.
What you get is a VERY customisable 'log sheet' for the planets you create and visit in your game. It is mostly eye-candy, but the sort of eye-candy that helps your game come to life, helps the shared belief in your alternate reality that you seek to create around your game table.
By cunning use of the 'layers' options within PDF technology, you get to customise the display of a main world and up to five moons. You can also tweak the background. Then there is space to type in planetary details, or you can print out the sheet and write on it instead.
It comes with a fairly straightforward instruction sheet. The one thing they've omitted is to remind you to save each planet you create as a separate PDF (just use 'save as' and give the file a new name) or you will end up overwriting one design with another! They also make casual mention of saving a PDF without the extra layers, to make one that opens quicker (especially on mobile devices) but don't say how you do that.
It's really fun and I must close my copy now or no more reviews will get written today!