Disappointing Image Quality

Dusky:

That's for the first hand information on this type of printing. The iPhoto preferences for books are:

Default DPI Settings in iPhoto 6's Preference File
BookTargetDPI - 300
BookTargetImageDPI - 150
BookTargetMediumDPI-300
Book TargetMediumImageDPI - 150
BookTargetSmallDPI - 300
BookTargetSmallImageDPI - 300
BookWarningImageDPI - 180
PrintImageDPI - 720
PrintWarningImageDPI - 140

Changing the dpi to 300 for the large and medium book image values seemed to improve image quality for users. Changing them would create the PDF file with that 300 DPI for the images as we understood. Does this seem to hold with what you know about the printing processes used? I haven't ordered a book in over year so don't have any recent comparisons.

Do you Twango?

Tutorials

How does one change the dpi? I couldn't find that option in iPhoto Preferences...

You use Pref Setter to open the iPhoto preference file and then search for "DPI". The values can then be edited and saved.

You're right. I was looking at my iPhoto 5 preference file. Since I use both versions, the pref file changes each time I switch between versions. Does get confusing at time. There is no need to edit the V6 pref file as it's at the max dpi that the printers are supposed to be able to handle. Thanks for the heads up.

We do not have Kinkoes or Lulu in the UK, so I cannot comment on the quality. However, if they use the same hardware as mypublisher et al, then the quality will be more or less similar - making allowances for operator/press variences. Should the iPhoto books not meet your quality expectations, then I would say you are pretty much stuck - as the other options with better image quality rule themselves out by virtue of the fact that you will need to order a print run in excess of 1000 copies. It could take 500 impressions just to set the run up. Will short run (single figures) digital press technology improve in the next year or two? - the answer is no. As I said, get to know a printer who can help you get the best out of the current technology. The technology is great - as long as you work with it, not against it. Higher contrast images print better, try not to have too many subtle tones and gradations or areas of flat colour - the busier the better. Saturated tones also print better than washed out tones. Experience is what you need - make notes and see what works and what doesn't.
As for the preferences - these could help, but are only worth changing if they are below the capabilities of the press. If they are much higher than the press requires, you are wasting bandwidth/network time and RIP time as the images get resampled by the press software. In reality, one of the biggest problems is Apple not giving us press technical information to make informed decisions about the image settings. In the early days of scanning, Kodak used to say that you needed to scan an image at a resolution that equated to 1.5 to 2 times the screen ruling of the press at 100% output size. In other words, assuming the image is at 100% output size, you need to set your dpi at between 1.5 and 2 times the screen ruling of the press.

I know from my experience the large, hardcover books were very good. The intended audience were parents of the child, our grandchild, that the book was about. It took an 8-10X eye loupe to see the halftone pattern.

The medium books were another thing altogether. The halftone pattern was visible to the unaided eye with strong light. Again, for the intended use, a memory book of an family outing, it was more than adequate.

If you're looking for coffee table photo book quality then you won't get it. As Dusky pointed out it's an entirely different printing process.

If you're looking to create a portfolio of your work to show clients than something like http://asukabook.com/ is what you are looking for. It's a very high end book printer and the pages are user designed with Photoshop.