The Bible's words are God's Word's (2 Timothy 3:16), so what better thing to prayerfully study than the Bible? Here are some resources that might be helpful. As always be discerning.
Pen and Paper: Buy Online
I.H. Marshall, A.R. Millard, J.I. Packer & D.J. Wiseman eds., New Bible Dictionary, (IVP, 3rd edition 1996): Buy Online
Baker's Evangelical Dictionary of Biblical Theology
Vine's Expository Dictionary of New Testament Words
D.A. Carson, R.T. France, J.A. Motyer & G.J. Wenham eds., New Bible Commentary, (IVP, 4th edition, 1994): Buy Online
Matthew Henry's Complete Commentary
John Calvin's Bible Commentary
C.H. Spurgeon's Treasury of David (Psalms)
Monergism.com Commentaries Directory
John Calvin, Institutes of the Christian Religion, (1559)
Chambers Dictionary & Thesaurus
Bible Reading Plans
I saw more clearly than ever that the first great and primary business to which I ought to attend every day was to have my soul happy in the Lord ... the most important thing I had to do was to give myself to the reading of the word of God and to meditation on it, that thus my heart might be comforted, encouraged, warned, reproved, instructed; and that thus, while meditating, my heart might be brought into experimental communion with the Lord.
George Muller, Autobiography: A Million And A Half Answers To Prayer, (2nd Ed. 1906), p.152