A short one! This book on prayer by R.C. Sproul is less than 100 pages and was on my shelf for a while.
Also, spoiler alert, the answer is YES. Still read it, though!
Favorite Quote: “If God never grants us another glimpse of His glory in this life, if He never grants us another request, if He never gives us another gift from the abundance of His grace, we still would be obligated to spend the rest of our lives thanking Him for what He already has done.”