No, I didn't mean that sin was the obstacle. If sin prevented belief there would be no believers.
I think the little truths that may need to be surrendered when the big Truth is found vary from person to person. As for myself, I had to get past the idea of a legalistic and judgmental God who could only be accepted or understood through formal religious channels. I've read that some people feel that life is to be experienced to its fullest and that spiritual devotions are too restrictive. Others have problems with "Why does God let bad things happen to good people?" And, of couse, many are unwilling to be Christian because they know some thoughtless, unethical or violent people who are Christians (or say they are). These are small "t" truths because each has some truthful aspect to it. But they are imperfect, flawed pearls.
For instance, you (and most people on earth) would probably agree with the statement that mirrors reverse things left and right. Have you ever wondered why they don't reverse things top and bottom? How does the mirror know which way the center of the earth is? Well, the truth is that mirrors don't reverse anything at all. We do. When we want to see how something looks in the mirror we turn it (or ourselves) around left/right. Try flipping a piece of paper end over end in front of a mirror and see what happens. Or better yet, in a brightly lit room write your name with a dark marker on a thin piece of paper and DON'T flip it at all, just hold it normally as if reading a book, then look up at the mirror and you'll see that you can read your name normally.
I know that was a long example, but do you see how it's easy to take things for granted that just aren't true? Try to think through deeply and carefully your objections to belief in, or devotion to, God. And as I said you'll want to look at what others have written on the obstacles you are encountering. Of course, there are tens of thousands of books on this topic, but if you narrow your thought to one objection or doubt at a time and get advice from others, you may save a lot of time and end up with greater clarity of thought.
As for the books I have read which have helped me, I must state first off that just because I found them helpful does not mean you will. And I'm NOT saying these books are pearls of great price! I'm just saying that they made some good thoughtful arguments that helped me to let go of the flawed pearls or helped me in my search for the pearl of great price. And of course, we're different people, you may not like them at all. And I bet some people will find things wrong with them, which is OK, I'm not saying that they're perfect, only worth consideration.
For the question of free will and God allowing evil in the world, I think the best thoughtful consideration I've ever read is Raymond Smullyan's "Is God A Taoist?" which you can find in a book called "The Mind's I" edited by Douglas Hofstadter. It's also available on the Web at
http://www.mit.edu/people/dpolicar/writing/prose/text/godTaoist.html
On the question of the very poor behavior of Christians I think C. S. Lewis' "The Screwtape Letters" is both VERY thoughtful and VERY entertaining (that's a combination you don't run into often, huh?)
On the subject of how very deeply God cares for each of us and how religion can <sometimes> interfere with that, my favorite book is Joseph Girzone's "Joshua".
To attack the idea that being a Christian is a gloomy and limited life, I love the book "They Found the Secret" by
V. Raymond Edman.
I have many other favorite books. There is, of course, the most popular book ever published: The Holy Bible. And there's Oswald Chamber's "My Utmost for His Highest." But at this point my suggestion is you work on getting past your doubts.
I hope this was of some help. May God bless you with wisdom.