In the spirit of Bridget's 'getting started' post about illumination, here are my top references for learning calligraphy.
There are dozens of 'introduction to calligraphy' books (just like 'learn to knit' and 'starting quilting'), and they won't steer you wrong. Almost every one starts with pen, ink, paper, and posture, then goes on to scribing X, O, 'thick' and 'thin' lines, using edges of the nib, etc.
These three are my favourites, because they refer to medieval examples to model on, and you can find them cheaply online (Abebooks comes through for me).
Medieval calligraphy, its history and technique, by Marc Drogin. Dover Publications, 1980.
This book is the 'workhorse' of calligraphers in the Society since it was published.
Pros: It stands the test of time because the author examined, and published, examples of original manuscripts alongside his suggested how-to models (the sequence in which you write a letter is called the 'ductus'). So you can see the originals, next to his suggested versions, and decide for yourself if that's the best way to create each letter.
Cons: you may not agree with all his interpretations.
The Art of Calligraphy, a practical guide to the skills and techniques, by David Harris. DK Publishing, Inc., New York, 1995.
Harris is also author of The Calligraphy Bible, a ringbound book with dozens of sample hands, and much of the same instructional content, but not in colour. The 'bible' is the one I refer to the most...partly because it's easy to prop open on the table next to me.
Pros: Art of Calligraphy is illustrated in colour, which is very appealing, and covers a lot of historic hands.
Cons: Fewer references to medieval examples than in Drogin, so you don't know what model the ductus is based on.
Historical Source Book for Scribes, Michelle P Brown and Patricia Lovett, BL, 1999.
This is a beautiful book from the British Library, drawing on their top manuscript expert and top practicing calligraphy and illumination artist.
Pros: Careful thorough reviews of exemplars, to describe each hand, drawn from the BL's collections, right down to analysis of angles of each stroke.
Cons: This meticulous approach could intimidate someone new to calligraphy, rather than inspiring them; the manuscript examples are the highest examples of the art.
Frankly, I'm more inspired by the 'average' book samples online than the pinnacles of perfection; it shows me that medieval scribes ranged from ordinary up to the extra-ordinary. YMMV.
These books are in English and most of the exemplars are English, French or Latin. I'd be very glad of some similar book titles about German, Swedish or other source-language calligraphy. Each region has its own distinct characteristics, and I'd love to learn more about them. Please add any favourite titles in the comments!