Phillip Yancey’s book “Prayer; Does it Make Any Difference” Is currently on sale for the Kindle at the price of $3.99.
If you struggle with doubt, with prayer, with Christianity, then I urge you to read this book. It was a key book in opening my mind up to the possibility of there being a God. Yancey does not mince words, he is direct in his writing. I often felt, while reading this book, that Yancey was writing and addressing my questions personally.