Start with high-confidence mutual funds & etfs books, then narrow by subgenre or adjacent topics.
Bogle on Mutual Funds
John Bogle
The Right Way to Invest in Mutual Funds
Walter Updegrave
Morningstar Guide to Mutual Funds
Christine Benz
Mutual Fund Industry Handbook
Lee Gremillion
The Only Investment Guide You'll Ever Need
Andrew Tobias
Bond Investing for Dummies
Russell Wild MBA, Steven Jay Cohen
The Little Book of Common Sense Investing
John C. Bogle
Investing Amid Low Expected Returns
Antti Ilmanen
Investing All-in-one for Dummies
Eric Tyson
The Income Factory: an Investor’s Guide to Consistent Lifetime Returns
Steven Bavaria
Common Sense on Mutual Funds, Updated 10th Anniversary Edition
John C. Bogle, David F. Swensen
Investing 101
Michele Cagan CPA, Michele Cagan
Your Perfect Portfolio
Cullen Roche
The Battle for Investment Survival: Complete and Unabridged by G. M. Loeb
G M Loeb