Lara Croft's most recent outing, Rise of the Tomb Raider, is currently available as the early access title in this month's Humble Monthly. It'll cost you $12 to sign up and get a copy, along with a set of other Steam keys that will head your way at the end of September.
For those of you with no idea what the Humble Monthly is, it's the name of the monthly subscription service offered up by the folks from Humble Bundle. For £10 / $12 each month, you get instant access to one game at the start of the month along with a stack of other Steam keys at the end of the month, before the whole thing repeats again the following month.
Signing up right now will get you Rise of the Tomb Raider and a bunch of other stuff in a few weeks' time. You can either cancel your sub then or let it run and see what next month's games are like. Your call.
Last month’s instant access title was Killing Floor 2, which was followed by The Banner Saga 2, Momodora: Reverie Under The Moonlight, Worms WMD, Stories Untold & OST, HackyZack, Eterium, and Volantia: Kingdom in the Sky at the end of the month. We don’t know yet what games are to follow in September, but they're usually worth over $100 collectively.