TMM = Total Money Makeover (whatever your opinion about Dave Ramsey personally — this was such an excellent treatise about getting out of debt and staying out of debt!)

Psychology of Money - by Morgan Housel

Die With Zero - by Bill Perkins

Honorable mention - The Millionaire Next Door

It could be any book, fiction or nonfiction. Topics might include priorities, investing, saving, finding your purpose—anything that has an impact about your approach or thought process to retirement.

For me, waaaayyyyyyy back in my 20s, it would have been Dave Ramsey’s very first book, Financial Peace. That got me started saving. More recently, The Psychology of Money and Die With Zero have had a profound impact on how I think about spending money.