There is a book by Paul Jeffers that is excellent.
Cover of book by H Paul Jeffers
Theodore Roosevelt Jr.: The Life of a War Hero
by H. Paul Jeffers
ISBN 9780891417392
I just purchased a used copy of this book for just under $4.
New copies go for about $25 or more.
Website BookFinder.com is an excellent website that gives you multiple on options on buying books since it is a book DATABASE.