How can two totally different books have the same title?

There is no copyright on titles. Once in a while you'll even see two books for sale in the same section, with the same title.

Publishers don't generally know the titles of the books other publishers have in the works.

Very simply, because there is no copyright on titles.

Book titles are not subject to copyright protections and can only be protected under trademark laws if related to a series (as trademarks are for "brands").

because they can - it's not like they're going to be by the same author

Put out by two different publishers representing two different writers
Two completely different genres for the books
One book may be out of copyright (older books have this happen)
Published first in another country then here
etc.

https://www.flavorwire.com/376237/the-doubles-10-pairs-of-great-books-with-the-same-titles

Why not?
You can write about different things and end up to have a same title you think best describe your book.
There's plenty of them.

For example, this is a recent read of mine, 
https://www.goodreads.com/book/show/49750133-finding-identity
It is a poetry book named Finding Identity.
It talks about the author's search for who he/she is, with different poems and proses that expose to different topics and other areas of life, and each of them approaches to the inner self

This is another book named Finding Identity
https://www.goodreads.com/book/show/14306166-finding-identity
It is a book of short stories about the struggle of human existence and how an adult try to fit in to the society

A single-word title for books would be even more common. Like the word "confession". Here is a whole list of them, the stories are all different:
https://www.goodreads.com/search?utf8=%E2%9C%93&q=confession&search_type=books

You can't copyright a title, especially if it's drawn from something like a poem or song, as many titles are.

"One Fine Day" is a title used several times.  It was inspired in most cases by Puccini's aria "Un bel di" in his opera "Madame Butterfly".

Because English only has roughly a million words and only a couple hundred thousand are in use, but there are a hundred thousand books published in the US every year.

You may now pretend you did the math.

For the same reason that you wrote "How can two totally different books have the same title" twice. Hope that helped. Hope that helped.

Why not. Wodehouse once said he was quite pleased with his choice of the title "Summer Lightning" - until he found so many authors had used it that he claimed he was entering his work in the competition for the fifty best books called "Summer Lightning."

It like others have said titles can't be copyrighted. But the book's subject, main plot, subplot and characters can be. Some time the books can be in the same genre also and it fine.

These are books I have seen with the same title, but by different authors.


An Agent in Place by Robert Littell 
Agent in Place by Mark Greaney

Against All Enemies: Inside America's War on Terror by Richard A. Clarke
Against All Enemies by Tom Clancy with Peter Telep 
Against All Enemies (A Jonathan Grave Thriller Book 7) by John Gilstrap 
Against All Enemies (Nathan Dixon Book 2) by Harold Coyle 

Black Sunday by Thomas Harris 
Black Sunday: A Novel by Tola Rotimi Abraham

Hunter Killer: A Pike Logan Novel by Brad Taylor
Hunter Killer by Patrick Robinson   

The Enemy Within by Larry Bond
ENEMY WITHIN (A World War I Thriller) by Mick Bose
The Enemy Within (Ravenloft) by Christie Golden  
The Enemy Within (Warhammer Novels) by Richard L. Byers

ship of fools, and the eternal city, have been used many times without any copyright infringement.
when i hear music or read books, i can see section of music that have been lifted from classical works, or when reading i can see that some parts of story plots have been lifted completely from older works.
it is possible no-one cares, as they are full of the need to win by writing a creative work; which also means "bucks".
generic works such as boy-meets-girl, and so on, are cultural property belonging to all, universal plots that can not be copywritten.

Definitely, I have seen 2 different novels with each the title "Billy" by 2 different authors.  There are no copyright laws attached to book titles so this is not a form of plagiarism. However, it is not recommended either as it is best that authors try to remain as original as possible.

Different topics, such as The Alchemist by Coelho and The Alchemyst by Scott, about Nicholas Flamel, a real person who is also used as a character in Harry Potter.

it's the same book. different covers.