I have been searching for this for a while now after I finished watching the series a week ago, but I can't find a rough answer on Google and sites such as answers.yahoo.com about which chapter of the manga picks up roughly around the end of episode 25 of Attack on Titan.
Which manga chapter will be a continuation from where episode 25 left off, and how accurate will it be? Does anyone know?
May I assume you meant in "which chapter"? Because if we said "which manga", well, surely it's in the main manga, Shingeki no Kyojin. True that the series now has many spin offs, but the anime is based on the main series, and as far as I remember, all of those spin offs came out after the hype caused by the anime.
According to Shingeki no Kyojin Mangaupdates Page:
Anime Start/End Chapter
Starts at Vol 1, Chap 1
Ends at Vol 8, Chap 34
So you can start at chapter 35...