Uncirculated Set Values

There is book called the Red Book by Whitman Publishing. In that book there are approximate values for those sets. Just remember those only approximate values and usually on the high side.

US mint and proof sets from the 1950s and earlier have held up their value fairly well, but those especially from the 70s, 80s, and 90s are only worth a few bucks each; like $3-5 for mint sets and $5-10 for proof sets. Check completed listings on ebay for a good idea of what sets really sell for.

There are some sets known to occasionally contain rare varieties or errors; you can find most of these in an old copy of the RedBook. If you only have sets up to 1990, go for the cheapest copy of the book you can find that is from at least the mid to late 90s - a ca. 2015-2018 edition should only cost a few dollars by now.

By books of nations, do you mean the Krause world coin catalogs, or do you have foreign mint sets? The Franklin mint did a promotional "Coins of All Nations" set of foreign mint sets that are fairly popular.