Infinity was created by RPG-players. Anyone that's played it knows how much detail they get into with the rules for what you are able to equip your forces with, along with the various combat situations in the game (I remember when I did my review of the previous edition of the rulebook I came across the chart for "lobbing a grenade over a wall that you can't see over"). The RPG is going to expand on that even more with lots of new books. Want to get those books in pdf as well? There's a new pledge level for you.
If you've already got another pledge level picked out but want to add pdfs of all the books that are going to be unlocked, plus whatever comes out for the next couple years, this add-on is for you. For £60, you can bring that in on your pledge. That saves you about £40.
The campaign continues on with 26 days left to go.