I have some impressions based on a rapid 'riffling' through the book, plus starting to read it from the very first page. In general, the book has interest for me: it keeps me reading. The illustrations (by Marc de Vinck, right?) are a bit of a surprise for me, since I was expecting to see photographs. They add interest to the book. Marc's illustrations make me recall with some delight the illustrations in a Rodale Press book, "Pirating Plants", which I bought when I was 18 or 19. (Umm...that was a long time ago, folks.) I loved the illustrations in that book. So the illustrations we see here certainly get my attention. I'm not sure whether there should be some photographs added. I'll reserve judgement at this time because I can hardly say I've read through the entire book.
I wish the book has an index! I wanted to quickly check if there are multiple pages discussing a real time clock, which might lead me to an installation procedure for that. Is one present, since you mention it as an accessory?
Page 4, "F. Status LEDs" is accompanied by Table 1-1 which is great. Some other bits of hardware might benefit with tabular lists of specific details, too. "A. The Processor." on page 2 could certainly benefit from this; perhaps change the text to "A. Onboard Processor and Video Chipsets" and accompany it with a table listing the exact model numbers of these items plus a link to reference manuals for each. Links to chipset reference materials could alternatively be put under under "Going Further", on page 17.
Page 5 is a bit confusing. It starts with list item "H. Composite video out." and "I. Power input." which reference the illustration on page 3. Then pow! Without a heading to introduce it, we have a new illustration, Figure 1-3, with new list items A through D. The illustration needs a heading that reads something like: "Power and I/O Pins, Version 2 PCB". Isn't that a Version 2 board we see in Figure 1-3? You ought to show an illustration of the Version 1 board as well.
Pages 6 and 7 make no mention of the specific USB cable needed for the power connection. Would you believe I bought the right charger for it, but the wrong USB cable? Apparently, a "MicroB" connector is not the same as a "MicroUSB" connector. That fooled me good. It will be a couple days of shipping time to fix my mistake with a new cable. Perhaps you should show an illustration of the exact cable connectors so that even old guys like me will get it right the first time.
Page 11 has a big sidebar box on Bittorrent downloads. With the small page size of the book, I don't understand why so much space has to be devoted to Bittorrent. These days, downloading the compressed zip file is about a 4-6 minute wait which is not at all bad. So I don't really see why Bittorrent needs a shout in Chapter 1. Couldn't that go into Appendix A? Perhaps mentioning that doing an sha1sum on the zip file and comparing that to the sha1sum published by the provider would save a lot of unhappiness when the user tries to put a partially downloaded image on the sd card and then wonders why nothing is working.
That's all for tonight...I'll say more in due course...