So, I thought of the question "What book could be described as 'Watership Down' meets 'Lord of the Rings'?", but I suddenly felt sure I didn't make up that comparison myself. So I googled [mystery title] along with "watership down meets" in quotation marks, and got:

[Mystery title] is Watership Down meets Ivanhoe!
[Mystery title] is Watership Down meets Rambo!
[Mystery title] is Watership Down meets Harry Potter!
[Mystery title] is Watership Down meets Conan the Barbarian!
[Mystery title] is Watership Down meets The Hobbit!
[Mystery title] is Watership Down meets Samwise Gamgee!
[Mystery title] is Watership Down meets Mighty Mouse!
[Mystery title] is Watership Down meets Chronicles of Narnia!
[Mystery title] is Watership Down meets The Voyage of the Dawn Treader!
[Mystery title] is Watership Down meets Tolkien!
[Mystery title] is Watership Down meets Tailchaser's Song!
[Mystery title] is Watership Down meets Godzilla!

I'm quite, quite sure you'll have no trouble guessing the "mystery title" after all that.