The Textura letter forms would have been more familiar to readers at the time, and were used widely in German until surprisingly recently. Even today we use them in English-speaking countries for short pieces of text that need to look authoritative. See the header of the manuscript of the US Constitution or the masthead of most old newspapers.
More importantly, these shapes looked similar to the letterforms from expensively hand-written bibles of the time. Different scripts take different amounts of time to write. A script like this written by hand takes an enormous amount of time because every stroke doubles back on itself. So only quite expensive books would be hand-written in this way. Of course, when you're printing, it makes little difference, so might as well print with the most-expensive-looking letterforms.
Here are some alternate scripts used in English writing around the same time: http://isites.harvard.edu/fs/docs/icb.topic453618.files/Cent...
(Source: wife studied paleography at Oxford, we have lots of fun books about this. There are far, far worse hands to decipher than textura, some scribes were truly terrible. You can also date manuscripts based on small characteristics of the hand-writing. Although, it can be a bit inexact. My wife once corrected a museum placard dating a text based on the writing. The docent argued with her about the characteristics of the script before she pointed out that the text mentioned a Saint born a century after the supposed date.)
Edit: Since you seem to have a convenient source there, could you link to some of the better medieval manuscript repositories online? Bookmarks got lost over the years.
obviously lucida console
While the typeface has some issues (m, n, u, i all look confusingly similar when next to each other, for example) I think the issue may just be that you are not used to reading it. This particular typeface is about 500 years out of fashion so you were never really confronted with it.
Some letters, like the ſ, aren't that easy to get used to, but when you do get used to them they actually help you (or, well, help me) read faster. That is, I think, because letters with an ascender are easily identified, and ſ (a different form for s) is actually very common in those texts.
One really interesting thing is the way that writing and reading have changed more than one might expect. A few anecdotes:
- Until some time in the middle ages, scribes did not consistently use spaces to designate word breaks. This was apparently an innovation of Irish monks. But it had important implications. Sounding out a string of letters is quite difficult. Our modern reading speed depends on the characteristic shapes of words, which only emerged once spaces were used consistently.
- Until relatively late, reading was a laborious process. And because the only things important enough to be written were worth reading slowly, no one much minded. One charge laid against the Jesuits was that they had developed a sinister method of reading silently rather than out loud(!) which allowed them to read much more quickly.
[0] http://www.amazon.com/The-Stroke-Writing-Gerrit-Noordzij/dp/...
I'm guessing you don't have kids - it was quite an eye-opener for me when my eldest learnt to write before learning to read: I'd always assumed writing was harder than reading, and that both were intimately linked... They're definitely separate skills.
[1] https://en.wikipedia.org/wiki/File:Jenson_1475_venice_laerti...
In reality, the respective difficulties were far harder to prove than one might think. First more rigorous scientific testing using tachistoscopes in the early 1900s/1910s provided more conclusive evidence beyond the anecdotal that Antiqua typefaces were indeed faster to parse than Fraktur. Until then, many people who were more commonly accustomed to reading blackletter simply thought it easier to read. Much of this has to do with accustomisation. If you are used to reading Antiqua, you will be faster, if you are used to reading Fraktur & Sütterlin but only encounter Antiqua every now and then, you will probably be quicker in reading the former.
In any case, Fraktur probably would be a lot easier to read than old-school blackletter hands— look at the sheer number of strange ligatures and abbreviations in the Gutenburg bible!
This is entirely based off of memory so I could very well be wrong. The fact that blackletter originally evolved as a way of condensing text, though, is pretty much indisputable.
Does anybody know what the purpose of the red marks in some of those letters is?
It looks here like it's setting off the first letter of each verse, rather than having the verses numbered. Because sentences start and end at different places in different languages, finding a specific verse requires the book marking where one ends and a new one begins.