I have War and Peace in txt format- (1296 pages in the physical hard-cover version I have- about the longest book I hope I ever read); the Archos opened it and I could scroll down while it was loading as fast I could read- I never hit the bottom of the file. It loaded the whole thing in 2 minutes. Unfortunately, the scrolling is a little slow so once I get to chapter 22 and have to shut off the Archos to take a break-- it will take 10 minutes to scroll back down to the page. I didn't keep any in html version - since the txt seem a slight bit faster. (The txt file will only be smaller that a html file by a tiny bit, unless the html is actually marked-up with bolds and italics and such I believe)
I suspect that perhaps the text version is faster because it has hard line breaks at the end of each line. This will have the effect that the browser will just display the text line-for-line as it appears in the file. HTML has to be reflowed to fit the page with, which means working out how long each word is, etc. This takes a bit of time.
The problem I had with long text files was finding my place in them after the browser has been shut down. You're not going to read War and Peace in one sitting, I guess
If you're half way down, it's going to take a few minutes to load enough text, then potentially a long time to scroll down.
That's not the fault of the 605, necessarily -- browsers just don't make particularly good eBood readers, compared to real eBook readers.
To be honest, I've never been able to use a 605 or similar device for reading books after I bought a Sony PRS. The PRS has an opaque screen which works best (rather that worst) in direct sunlight, and a 700-page battery life.