I got this book about 5 years ago shortly after it was released. It was the first book specifically dedicated to melody writing that I'd ever read but since then I've read a number of others (including Berklee Press' own Songwriter's Workshop: Melody). I must say, "Melody in Songwriting" is still the best book on the subject that I've seen!
It covers an awful lot of ground and goes into greater depth and detail than many other books on the subject of songwriting. In fact, this is a valuable resource for composers in any style of music, not only songwriters. Granted, beginners will likely feel a little intimidated at first, but I say, 'just reread it again', what you'll learn is more than worth the effort.
Melody in Songwriting includes about half-a-dozen well known songs as examples plus a greater number of unknown but insightful examples. This brings up the books' one weakness, which is that no CD of the examples is included so in order to hear and fully appreciate the given examples you'll need above average music reading and keyboarding skills. Perhaps Berklee Press will consider releasing a CD addendum to this excellent book.
Bottom line; if you read this book and do the exercises, you'll be able to write a reasonably good melody every time you sit down, even without inspiration. Add inspiration and you just may write a great melody.