We've mentioned this before, but the Scott US Specialized is the one book you need to help navigate the many varieties of US stamps, embossed envelopes, postal cards, basic revenues, local post stamps, provisionals, private die proprietary (match and medicine), and on and on. You may not need a current catalog, but even for identification of material it is not wise to buy too old a cat. The expansion of knowledge, varieites, collecting categories, and such will leave you behind. For example, that 1987 catalog that Peter mentioned does not show a single postage stamp essay, to say nothing of all the stamps issued since 1987 (many hundreds of stamp listings). Nor does it make note of the I-grill varieties on the Banknote issues, which are easily encountered on
ebay, but not always recognized by sellers. The I-grills are mentioned in the older catalogs, but the listing of the I-grills as major types did not start until 2013. Those are just examples of the kinds of new listings and research that the old catalogs do not have, yet none of this has anything to do with pricing. The Specialized is much more than a pricelist, and I suggest you get one that is not more than 3-5 years old. For what you collect now, and for what might spark your interest if you only knew about it.