Voyages is great for solo play and is loaded with encounters and adventures and characters that can come up in solo play hexploration. It has everything you need for solo play pretty much built in. No prep needed. Just roll and go and see what happens.
Should you ever find yourself asking "now what?" roll the Situation Dice. And if you are ever uncertain on anything, you can always Ask Starry.
If you do find yourself wanting more tools to generate even more stuff, then the TNG guidebook is a great additional toolset as well to have on hand, but it is not necessary to play.