Trollope, Anthony: An Old Man’s Love, v. 1, 21 April 2008.
 

(1884)
Trollope’s last completed novel, finished seven months before his death and published posthumously. (It recently appeared on PG).
A young woman must choose between two suitors. One of them is not young… However, he’s only 50 (--the prime of life, in my opinion).


From the summary at Manybooks.net:
‘50 year old William Whittlestaff becomes guardian to Mary Lawrie, the orphaned and penniless daughter of an old friend, and finds himself falling in love. But Mary has already given her heart to John Gordon, who returns after three years' absence, on the day of Whittlestaff's proposal.’