Yeah, it has been updated to include some of the modern weapon systems and tactics. It's a dry read for sure.
While its not free, we also utilized "Ultimate Sniper" by John Plaster. It's easier to read and has better illustrations and has more resources and information than 23-10. The Ranger Handbook (SH 21-76) is another good resource for field craft. You can easily find it online since it is an unclassified Army publication. You can also pick up a hard copy for a few bucks. It reads more like an outdoor guide than a military publication.
Or if your MIL/LE just download the new Army Sniper TC that has been revised to include more content on field craft. Link is in signature. If you want additional field craft material, by far the best book out is by CROPS Covert Training Manual which is a recommended reading source in the new Army Sniper TC as well.