Yes to both Peterson books.
Splendid Soups is practically the only book I actually follow recipes from. It's got like five recipes I like so much I make them over and over, so I've never even had a chance to try the other many hundreds. I usually double the seasoning ingredients ... Peterson has a subtle palette when it comes to spices and aromatics.
The Sauces book practically taught me how to cook. It's incredibly comprehensive on history, technique, and family trees of recipes, especially with the French stuff. Every French brown sauce-based recipe is explained with a classical version and a "nouvelle" version (one w/ demi-glace, one w/ glace de viande, thickened with reduced cream or butter).
It pretty much stops before all the sauce innovations of the last 20 years. Unfortunately the best source for those is the Modernist Cuisine $eries. I've talked to Peterson about working with him on an updated Sauces edition (he's a fellow Brooklynite). He's interested, but is unsure that a publisher would be. Apparently having written a dozen award-winning cookbooks doesn't give you much influence in that industry.
They get better all the time but I only really bake once (at best twice) a week. Been learning a lot for sure.
