I'm reading The Constant Gardener by John LeCarre and looking in Wikipedia for date of publication (2001) ran across the fact that it was loosely based on a true story. Now, it turns out I'm a frequent fan of such 'maybe almost true life books' and especially movies. Usually the extent of the 'trueness' of the movie is revealed at the end of the story.

It's often rewarding and adds to the emphasis of the story, which in itself interesting. But do any readers here avoid getting background on a story before reading? Do you think this is a type of spoiler? And does knowledge of a book being based on real events affect your opinion of the book in any way?

And finally, does anyone else often turn to Wikipedia, before or after reading a story to gain insight on its background?