Free Kindle Book: what should I buy?

[former player]

I've been given a free promotional code for a Kindle Book.  What should I get?  All suggestions, mustachian and otherwise, welcome.  I don't have a Kindle, so I'll be reading on my laptop.

I haven't read the Marie Kondo book yet, so at the moment that's my default option.  Other suggestions received with interest.

[GrowingTheGreen]

Millionaire Mind or The Millionaire Next Door - both by Stanley.  I believe The Millionaire Next Door is already free though...  Either way.  Great books!

Blackhawk Down by Bowden is still the only substantial book that I've read in 24 hours because I couldn't put it down.  Twice.  Not sure if you're into military non-fiction though.

[former player]

 I've asked for ideas on what to get because I've realised that my reading habits have become a bit predictable.  A free book code seemed like the ideal opportunity to shake things up.

Sol military non-fiction not usually my thing, but in a spirit of enquiry it's added to the list of potentials.  Thanks.

OK: Kondo and Black Hawk Down.  It'll be interesting to see what the Amazon algorithms suggest based on those two.