The digital copy of the report (original from "Harvard College Library" is absolutely riddled with badly copied pages, and even more concerning, with numerous duplicate pages, with no way to anticipate where these duplicates will appear. The original has about 1080 pages; this copy has over 2000. One supposes that original book does not have these problems, so it would be wonderful if Harvard could get it re-scanned. There is another online copy from the University of Minnesota at Hathi Trust, unfortunately will all the restrictions Hathi Trust has for individual users. It is listed as public domain and Google-digitized, but I have not found it in Google Books.
Other than that, this is a wonderful treasure-trove of information about the Mexican War, as it unfolded, with descriptions of by the Topographic Engineers and combat units moving through the incipient State of Texas and Mexico, and a view of the workings of the 1840s U.S. Army. (But I discovered all that by reading the Hathi Trust copy.)