There are quite a few books in Taiwan on Daoism, though most of the ones in English are of the Daodejing and Zhuangzi variety. If you are daring, there are a couple of good histories out by Taiwanese scholars … look for any book with the title, “Zhongguo Daojiao shi”. I must apologize for the lack of Chinese characters in my post, but my OS is mainland Chinese (simplified) Win98, and I am not sure of the effect if I post here in BG. Anyways, soon enough I should be getting ADSL on my desktop, which will alleviate this problem.
As to good English books on Daoism, anything by Stephen Bokenkamp, specifically, “Early Daoist Scriptures”. This is a great book with an excellent introduction section explaining sects and their beliefs, followed by individual sections on specific texts. Very good stuff. Good luck finding it here though. If you really want it, I do have it here, we could make a trip down to a copy shop together …
As well, anything by Isabelle Robinet. Her “Taoism: Growth of a Religion” is a very good, although somewhat brief (only about 300 pages)history of Daoism. However, finding it here would be close to impossible, put I can only offer the same solution as above, or order both on-line I guess.
As to the “why” of Buddhism being somewhat more successful … I think it is a sad reality that Buddhism sells better than Daoism. Religion in the Mainland has for the most part, been permitted to exist because it seems to be good for tourism. Buddhism has a better track record (look at the popularity of the Shaolin si), and therefore gets more money, support, etc. Just my thoughts after living there for six months, but I think they are relatively accurate.