Thanks

Just tried Midori. Version 0.1.09 actually runs more quickly than 0.1.10 which is sluggish. It works and I can open locally stored HTML files but haven't gotten it on the Net. The 3G connection is only active when in the eBook Mall and when checking for new downloads, then it closes immediately.
Without Midori, there's HTML support. Though IREX doesn't mention HTML, I was able to open an HTML book stored on the card by tapping on it (accessed the file via SD card hack). Apparently it uses webkit to do this-- how interesting. Also slow if you're trying to read a full length book in HTML format. Really, really slow to load and then slow to scroll.