I am an unrated player who geats 1590 in rated games against fritz8 unleashed which is 2500 elo approx. [yikkesss!]

The area I am worst at is the middlegame? Any books I should read? Can I use fritz to help me?

I have trouble analysing exchanges and I often drift without a plan. If I can close up the board and get a positional game going I can do OK.