Myriad

This year's edition, Guiness World Records 2008, had this to say about the font used in the book:

This year's edition is set in Myriad Pro, a beautifully proportioned and highly readable humanist sans serif typeface designed in the early 1990s by Robert Slimbach and Carol Twombly (both USA). Humanist fonts are those that embody the cleaness and purity of a modern, "grotesque" typeface with the natural, organic feel of hand-drawn letters; sans serif refers to the lack of serifs or flourishes - such as the small feet on a serified n or i - common to the "roman" typefaces.

That was...s-so beautiful. *sheds a tear*

Although admittedly I didn't know that bit about the sans serif.

I searched for "Myriad Pro" and it turns out that for $35 each you can choose from a whole myriad of styles of Myriad Pro, such as: Regular, Condensed, SemiCondensed, and SemiExtended, not including all the Bold, Black, Italic, Light, and SemiBold variations.

The website also adds:

Myriad also has subtle geometric shaping and monotone color, balanced by varying letter widths and open counter shapes. A readable and friendly face, Myriad works well for both text and display typography. A headline font and the playful "sketch" and "tilt" versions add versatility.

This is clearly the BEST FONT EVER.

I think I haven't had enough exposure to the world of "professional font-making".