What is your goal, exactly? If you simply want to learn how to write basic (and short) sentences quickly and correctly, you should probably get something other than a prose composition book.. most composition books are complex because they cover technical stuff for more experienced students, which you might not want yet.
Instead, perhaps you should try Lingua Latina: Pars I. Have you ever seen it? By the time you finish the readings, exercises, etc., you will be able to construct basic Latin very easily and quickly, and can then move on to something like "Bradley's Arnold" with confidence.