Well, it’s not the best way to go about it, but I did the same thing on my first fonts. The glyphs in a font are built on a grid and all the anchor and control points need to be centered on the intersection points of those grids. There’s also the issues of sidebearings (although monospaced fonts are easier), hinting, OpenType features and about a million other things that can’t be addressed in Illustrator. It’s gotten to the point where I no longer use Illustrator at all when building fonts and use Glyphs and FontLab.
I’m not sure there are any good books that will walk you through the process, but as for general books about typography, there’s The Elements of Typographic Style, which is something of a classic. There’s also Gerard Unger’s Theory of Type Design that I bought last year when it first came out and have neglected to get around to reading it.
No, it’s not a secret, but I’m sort of embarrassed that it’s taken me so long. I posted some examples of it over a year ago here saying it was about done. Then I decided to expand the character set, do the italics and design three separate widths in addition to the seven weights of each width. And this meant that I could make a variable font with two different axis, which added additional complexity to the projects. Like I said, it’s been a beast. Here are some examples of the upright weights, though, minus the italics and all the other special characters, like numbers, symbols, punctuation, European diacritics, etc. I still need to adjust the hinting on some narrowest, boldest weights to keep the counters sharp and not look like they’re beginning to fill in at smaller point sizes.