I would say about 2 weeks is the standard. However, this also depends on the length per day. I did 6 days of 12-hour shifts at a hospital for one of my WEx and I can guarantee you that's more experience than many who did 4-5 hour sessions at a local clinic. On the whole though, two weeks on paper.
Book are sort of.. eh. I can understand why smile stealer's is the top of your list, I think that's true for most dental applicants. For me, it wasn't very interesting of a read, and sure it was fine, but it wouldn't be something that I usually invest time in. Unless you enjoy history and the gruesome )some would say interesting) aspects of dentistry, I would say you should go do some searching on google on any interesting books on dentistry. If you're interested in the online and innovative aspect of dentistry, I'd recommend a great read called - An Introduction to Mobile & Teledentistry: How Technology, Consumer Demand & Prevention Are Shaping the Future of Dentistry - it is a little bit niche but it gives a good idea on how dentistry is evolving in terms of that. I would also branch out from dentistry. There are a far wider range of books suitable for your age on the medical field, ones which you can easily find online, e.g. When breath Becomes Air - Paul Kalanthi as suggested by ERCross above, This is going to Hurt (cliche but a must read), Do no harm Henry Marsh, all classics.
Articles on the BDJ are also... subjective. Reading entire issues of BDJ is something that I can guarantee you no dental applicant has done (and this is coming from someone who read a textbook on dental nursing). Read what interests you, most schools will have a digital account where you can access it. Hope this helps!