It's a wonderful book and has a huge amount of useful information, but there is one thing I will say as a new calligrapher just learning broad-pen (6 months experience).
Don't get too attached to Sheila's 'way of doing things'. She was a great calligrapher, but she frequently presents her method as the method. There are many methods, there are many 'right' ways to do calligraphy. While much of what she says is extremely useful, you're going to want to figure out what method works for you. I've found a practice method of attempting to write a sentence, then improve that sentence in the space below worked well for me, doing that over and over.
You WILL develop bad habits. You don't need to take someone as good as Sheila as the last word on calligraphy. There will be days where all you want to do is take a piece of trashy Warhammer 40k lore or a bit of scripture and write a few sentences in some real pretty script.
There is no failure state for calligraphy other than stopping. Even if you are continuing day on day, every day you're still doing calligraphy, you are a calligrapher.
Oh - regarding Sheila's bit on spacing - this is FRUUUSTRATING. While she's extremely right about the importance of spacing, the rules she adds for it are fussy and very precise. I found them discouragingly complex. To that end, I wouldn't even worry about spacing as a concept until you've got at least one hand worth of miniscules and majiscules to the point you don't need an exemplar to pen them consistently.
