I played the first fifteen mission of the Behind enemy lines, till I bought Men of Courage, so I am evaluating the tips from this book till the Mission 15.
First there is a brief introduction about the mission, and dividing them into phases, with little history.
There are a lot of detailed pictures, with soldiers numbered in the best order you should take care of them. The text is detailed, full with helpful advices and cautions, especially about tricky points in the mission (where you must hide the bodies, unseen patrolling guards, time limits). Also information about liberating allies, or using barrel, which it took me long time to figure out had I did not use this manual. You do not have to follow all the tips exactly, use your imagination and feel the challenge of "straddling in the combat filed". I did that in Mission 5 and 13.
It is a great help, and without the missions will take longtime to accomplish, so use and enjoy the Commandos.