What's wrong with learning to read from tunes?
Nothing is "wrong" with learning to read from tunes, strictly speaking.  It's just painfully slow going (years may pass with only slight improvement) because the pitch range is too wide, and there isn't enough repetition of the same note in close proximity to itself to reinforce visual memory.  It's like deciphering the note every time you see it instead of cultivating a physical reflex to produce the note at sight.  More about the hitches in the  fiddle tune approach.

 How does "Standard Notation for the Tab-Addicted Mandolinist" help a tab reader deal with standard notation? I would take it that the focus is to give a tab mandolinist a chance to play non-tab stuff like classical, etc. Is there more to it?
This book shows you how to stop struggling to read one note at a time and move quickly to recognizing musically meaningful patterns, relating them to your fretboard as you go.  Notes in music, like letters in English, aren't actually meant to be read one at a time. 

In addition, the book supplies a logical approach and includes structured repetition, with tips on pattern recognition. (The problem with learning to read from tunes is that it's hard to learn to read from things you recognize and can fudge by ear.)   I chose mostly classical material on the assumption that most tab readers don't already know those melodies.   In addition, "classical" music is constrained by very specific rules about how dissonant pitches may be approached and left.  These constraints, in addition to giving "classical" music its rather formal sound, are very useful for beginning reading exercises because the patterns are quite orderly.

The book also includes 'trad' selections, like 'simple gifts', and  I wrote a set of jigs and reels (tuneful enough to be fun) in the style of trad AABB tunes which are also good right hand technique builders since the moving pitch is restricted to one string.  Practicing them will entail structured string crossing.  It's also the case that certain intervals fall under the left hand more comfortably than others and I have incorporated this into the material.

 I already read treble clef pretty well, but I'm new the the mandolin.  Friends have suggested using a violin book to learn the fretboard.  Does your book offer anything a violin book doesn't?
While violin material may be perfectly serviceable on mandolin, it's not optimal. With my book, you will combine learning the fretboard with training your picking hand, and you will move through learning new pitches at a rate completely impractical on fretless instruments. I think you will find it optimizes your practice time quite well so that you can play anything you want in very short order, far more quickly than if you use violin material.

A violin book is a perfectly good way to learn the neck, though I would recommend a violin book (with etudes), not a fiddle book (with tunes) to get you up to speed in the shortest amount of time.  There are two hitches in using a violin book: 1.) much of the material in a beginning violin book is devoted to etudes that teach drawing a straight bow stroke which isn't applicable to mandolin and 2.) violin material will move more slowly through learning pitches because it is designed to cope with intonation/string-crossing difficulties not found on fretted instruments played with picks.

 I'm mostly interested in swing tunes.  Will you be writing a jazz version?
Even if your not specifically interested in "diatonic" music, it's actually easiest to learn to read in a plain old vanilla, diatonic key, with simple material, in simple rhythms, such as supplied in this book.  From there, it's a very short hop to "The Real Book".  The hop is short enough that it really doesn't make sense to write a jazz specific version.  The art of jazz, of course, is not to be found on any page.  But enough notation literacy to read the basic melody from a lead sheet will follow easily from completing this book. Other hitches in learning to read from jazz tunes.