I've been using an Epson "Perfection 1200U" flatbed scanner for about 2 years now. At the time, it was about the highest rated (per $) thing on the market that was only a "little bit" above my price range; but I'm sure there are other better ones out by now.
The Canon site (quick look only) doesn't give version numbers for the bundled software, but it should be safe to assume that it's all current. The LIDE20, and most of the other Canons I looked at, all seem to come with OmniPage Pro, which is the same program I got with my Epson - but probably at least two generations improved.
I use the OmniPage software almost exclusively when I want to save an image, and it's very good. It lets me do a preview, and if necessary, reposition and do another preview (or several) before scanning. You can select (rectangle crop) an area to scan, and "cut out" pretty much what you want for the image. Lots of choices on image type, and you can "tailor" a new "image type" easily if necessary. (I created a "hi-res lineart" setting just to copy wiring diagrams out of maintenance manuals – so that I can really blow them up enough to separate the wire labels.) The "de-screen" setting does wonders for images out of books, magazines and newspapers.
One "feature" of OmniPage that took me a while to sort out is that it attempts to save stuff as "multi-page" TIFF files. I don't have any other program that can open one of these, and it's a RPITA process to reopen in OmniPage just to separate out a single shot, save as a separate TIF – just to be able to paste into something else. I save each scan as a separate file, and select "new scan" (not "insert page") for the next shot.
I didn't find the OCR capabilities of OmniPage particularly impressive, although that may have been improved in newer versions. It was a toss-up whether it was quicker just to type a copy or to make the necessary corrections to the processed scan. I bit the bullet and bought TextBridge, which I use almost exclusively when I want an OCR conversion of text. A nice feature of TextBridge is that it puts an icon in your Office programs, and you can scan, convert, and insert directly from Word. The OCR conversion accuracy – compared to OmniPage – is spectacular, even if not yet 100 percent. The difficulty with the "direct import" mode is that you don't automatically get a preview to make adjustments – it's a zip-and-go process.
I'm not familiar with the ArcSoft PhotoBase software that comes with the LiDE20 scanner. Maybe someone else can comment. Unless someone can offer enthusiastic praise for it – my own two-bits worth would be that you should consider moving up to the Canon D1250U2F scanner – because it bundles Photoshop Elements.
If you are ever going to use a digital camera you want Photoshop Elements (unless you've already got PhotoShop 7), and it's a little over $100 US by itself. The $50 difference between the LiDE20 and the D1250U2F gets you a significantly better scanner – and Elements for free.
As to scanning books – there ain't no good solution. There are some bad ones.
The multifunction type monsters that everyone is selling are generally one of the bad ones, since they usually include an "automatic feed" for single-sheet scans. You can open most of them up, but the feed mechanism gives them a wide edge that makes it hard to position a book. As you guessed, a "thin" edge is something of an advantage.
For most book scanning, the real problem is holding the book in place while you make the scan. The ideal would be a big enough scanner to take "both pages" at the same time, but the next best is a support beside the scanner at the same level as the scanning surface. I made a "paper storage box" that the scanner sits on, that brings the scanner surface level with the Laser Printer that's next to it. For the other page, I place a toilet paper roll on top of the Inkjet on the other side – which holds the book at just about right height. The real problem is getting the page to lay flat, and that ain't gonna happen unless you "break the spine" on the book – regardless of what scanner setup you have.
Based on my experience, the Canon LiDE20 looks like a good package – with my above suggestion about the D1250U2F as a possible "think about."