Text File
I started off with simple text files containing book titles and series, primarily because the phone I was using at the time can open and save text files. My first safeguard against accidentally buying a book I already own. It was simple and effective enough, but as the number of books increased, it got a little unwieldy.
Photos
When I had to switch to a different phone, text files are out - the new phone couldn't use them. I resorted to taking snapshots of my book stacks. This "method" kinda worked (and worked for quite a while); it was just tedious to search through all the photos when I'm in a bookstore checking up a title. I changed them to screenshots of my text files - better, but only slightly.
Meanwhile, I converted my text files into a OpenOffice spreadsheet. I added even more details to my catalog - authors, ISBN, genre, read status, as well as when and how much I paid for a particular book.
Online Documents
When I started actively using Google Docs, I also migrated my spreadsheet online. Having it easily accessible is really great.
I also had a brief stint with Socrata (formerly blist.com), which is a social database kind of thing. It looked really good, but was a bit too fancy for what I used it for. It's Flash-based, so not as easily viewable on mobile devices. But Socrata does support export to email as html, which is a really nice feature.
Social Book Catalogs
Finally, I turned to online catalog tool, having gotten a little tired of having to manually type in book details (not to mention having gotten an urge to make what I've read public ;).
It all started when I discovered the weRead Facebook app. I started migrating stuff to weRead (via Facebook), but several issues irked me. I found the interface to be cluttered and not user-friendly, with information inconsistently shown. Its book and author database is also hopelessly messed up: incorrect and inconsistent book titles, incorrect or incomplete author names, and very poor handling of editions. You can't edit the book information and while you can upload your own cover image (many of which are missing or incorrect), it seemed buggy because some (strangely, not all, just some) of the images I uploaded disappeared after a period of time.
I started googling around and found several promising alternatives: LibraryThing, Shelfari, and GuruLib, of which I also found someone having done a simple comparison. I settled on trying GuruLib.
LibraryThing is only free for up to 200 books, so that's an immediate no-no for me. Can't see myself paying when I really just want a place to hold my book list so I can search it. It does possess a whole lot of features, even has a mobile version of its website. The UI is not particularly attractive though, compared to Shelfari, which looks good but Shelfari being tied to Amazon only seems unnecessarily limiting. It also doesn't seem to have any export feature or social groups.
GuruLib is simple to use, and unlike weRead, it allows you to edit book information (although changes appear limited to your account only). You can also add CDs, DVDs, games, and other software. You can apparently use your webcam as a bar code scanner to add your books or items, but I didn't try that - its import tool managed to import my list of ISBNs nicely. The interface is dated though, being little more than simple forms. Understandable of course, what with it being a homegrown project with only one or two persons working on it. It still didn't feel quite right as its shelving (i.e. categorising) options were rather limiting, and since I don't see it improving much any time soon, I started looking again.
I had the good fortune of seeing someone mention Goodreads on a blog comment (can't recall where) and that's what I'm currently using. It's been quite satisfactory so far and I'm glad I found it. It's a relatively new (2006) social cataloging tool and it already has a large number of books and users.
The best thing is that it's like a wiki, and the community itself helps to manage and maintain its database of books and authors. The way you can categorise your books is also very flexible. This translates to a much more accurate and consistent body of data. Even better is that you can add new books - perfect for people who have read books not published in the western half of the globe.
It's been a long post. Maybe I'll leave why I like Goodreads to a later post. If you join Goodreads, look me up on my profile (just realised I have a staggering amount of books to read!). Also check out the social group of Goodreads Malaysia.
Happy reading.