Never underestimate acting. I cannot stand hammy acting. Plus, don't think you have to reinvent the wheel; there is an entire field related to theatrical meaningful performance studies- drama and theatre. Obviously nobody has all the answers which everyone agrees with as to how performance should work and that's part of the journey, thinking and learning for yourself. For this end then, I could reccomend definitely:
-Stanislavski 'An actor's work' (A single volume which contains 'An actor prepares' and 'Building a character' I think you can get it off Amazon)- The master of the 'naturalist' school of acting- perfect for magic, in my opinion. Elementary text on acting theory.
-'Brecht on theatre' again, easy to get hold of, some great thoughts contained within. Elementary text.
-'Theatre and its double' by Antonin Artaud. Again, one of the pioneers of modern theatre and the 'theatre of cruelty'; elementary reading on theatre.
Well... as a matter of fact, there are many, many books in this field that I could reccomend, but whats all this about finding stuff out for yourself?

But look up some key people like Bertold Brecht, Artaud, Peter Brook e.t.c. and just have a google about these things if you're not prepared to invest time and money in books. Thinking about theatre will help you answer the questions about 'what should performance mean? What is it's role? How should it work?' and developing your artistic vision for Magic. All the greats have done this, not all explicitly through thinking about theatre (although in the earlier days of 'modern' magic I believe this to be so) but in some respect they all have- Tommy Wonder being the perfect example.
Of course though, there are some magic related texts. Darwin Ortiz' 'Strong Magic' has been reccomended, as has Juan Tamariz (I would probably reccomend getting every single thing you can find of Tamariz, but thats probably not very helpful) both of which are perfect examples. Nelms' 'Magic and Showmanship' would be quite an accessable and easy to get hold of book, too. Nelms, as I psychically predict Mark Lewis will back me up on, did not actually perform magic or prepare magic shows, but, he was a theatre director and if you know anything about theatre and acting it is incredibly obvious throughout the book. The insight is in how the book relates to Magic.
Finally, it will take 'time and experience'. But there may not be millions of books strictly related to magic/ mentalism performance philosophy (Possibly because there is no correct 'answer' per se) however, once you get used to magic literature you will find that authors tend to write their performance philosophy in there somewhere and offer advice on performance all over the place, which you will pick up as you go along. For example, if you know the age old classics of Harlan Tarbell's contributions to magic*, there is not a set section on 'this is how you should perform' which gives all his advice and the rest are just packet tricks... absolutley not! Performance advice rears it's head on every single page, every trick and every interlude and digression. To give another example, take 'Expert Card Technique'. By title you may assume that it is not performance philosophy related, but as will
all good magic books there is performance advice given all over the place and in this particular book, a chapter devoted entirley to presentation which is worth the books value on its own.
So- read around... think... stick with it... and
time, hard work and origionality always pay.
* If you don't, you really should! What Euclid is to Geometry (In fact, there are '13 books' to Euclid and the term 'Royal road' was first used by Alexander the great- I think- in reference to this this work!), the 13 steps is to mentalism, RRTCM is to card performance... the Tarbell course is to magic.
EDIT: I forgot to mention being entertaining. Perhaps the most glossed over aspect of performance theory. If you can't be entertaining, unless you are selling yourself as Jesus, there is no point in doing magic.
''To go wrong in one's own way is better than to go right in another's.'' Dostoevsky's Razumihin.