You might not necessarily need a book. Look back on your life. Contemplate on and consider the things you have done, the thoughts and ideas you have had. Do you find any common themes? By looking at your past God sometimes shows you the future.
Your life is a very good book to help direct you where God is pointing you. It’s also a very good book to point out to yourself where you might have rejected or blocked the way God was pointing out to you. Study yourself over the next few weeks. Read your life (no matter how long or short it has been). Spend time each day pondering it and be sure to write down any enlightenments that come to mind. Always pray to the Holy Spirit to guide your “reading” – He will show you if you are open to Him.
Finally, after a few weeks if you are still not sure, get your Bible, pray to the Holy Spirit and then, without looking at what you are doing, open up to a random page in one of the Gospels and start reading where your eye falls. Right after that open up to one of the Epistles and start reading where your eyes fall.
After all of the above you should have a pretty good hunch of what you need to do and where you are to go in life. The last step, however, is having the courage to take that next step in implementing it. Constant prayer will carry you on.