I bought the 3rd edition when it first came out, so the reviews weren't outdated like they are now. It was worth purchasing because I learned some important things about haircare formulations. For example, it is good to avoid drying surfactants (such as many of the sulfates) in shampoo. Since I have fine hair, I also avoid things that might build up and weigh down my hair, such as silicones and film-formers (e.g. acrylates, etc.) in shampoos. I've also learned to avoid two particular ingredients: ammonium xylenesulfonate (a very drying solvent, which is particularly prevalent in drugstore products) and sodium polystyrene sulfonate (which is very drying and can even strip hair color). And I learned that after swimming, I should use a product with disodium EDTA or tetrasodium EDTA to remove minerals. Now that Paula has taught me to read ingredients lists, I don't find her reviews to be a necessity, except that it's nice to know how much hold a particular styling product actually has (since labels are not at all accurate or consistent). <br><br> I don't always agree with Paula, however. For example, she seems to see no reason to purchase salon products instead of drugstore ones, but I cannot find a decent shampoo or leave-in conditioner at the drugstore. Paula also sings the praises of silicones, but these cause nothing but limp trouble on my fine straight hair, and I know many curly-haired people on the MUA haircare board also dislike silicones. Overall, this book was worth purchasing once, but if she comes out with a 4th edition, I doubt I'll purchase it.