I read computer books!
And know exactly what are you referring to, the code portion!
Actually, the reason why I bough the Kindle DXG and later the Kindle 3: Amazon ebook store for computer books.
The Nook was my 1st eink ereader but was I not able to find good prices and good titles on B&N; the good books (computer related) are being sold by O'reilly and Amazon.
Having said that, I like the Kindle DXG and most recently I am using the iPad and Kindle app.
Kindle 3 is surprising me these recent days because new ebooks are being formatted better for small screens, so the code lines do not cut off or wrapped around themselves. Do not worry about PDF books or format if you are buying new from Amazon. I find the books I want 99.9% of the time on Amazon, so I don't need the PDF format anyway. If not, I check on O'reilly and they sell the ebooks on mobi/epub/pdf format, a bundle, so will work anyway on the Kindle, no conversion needed, they are DRM free.
I suggest you the Kindle DXG as 1st choice and Kindle 3 as second.