I vote for buying PPLP, since you're already familiar with the concept of LCing. Nutrition is summed up at the end of the book; the rest of the book is really valuble info that's not entirely carb related. PP was good to get from the library, but PPLP is the one I prefer to keep.

It's also probably the one that the Eadeses would want you to buy: they were a little disappointed that their previous publisher 'pressured' them to turn PP into just another diet book. PPLP has all the stuff they really wanted to write about. Plus, new research caused them to change their minds on a few issues.

HTH.

(edit: ) BTW, "Protein Power" was the original book; the follow-up is "Protein Power Lifeplan: A New Comprehensive Blueprint for Optimal Health" published in 2000.