The last time we met, our agenda was to discuss IBHS ch. 22 (on the Qal) in the light of current thinking about situation aspect, especially stativity. During the discussion, we got held up for a moment by an English example that they use:
[S]tative verbs in English do not occur in progressive forms. ... [For example], one cannot freely say 'I am loving this book.' Since 'love' describes a stative situation (in this case, a psychological state), one freely says 'I love this book.' (IBHS 22.2.1e).
The students unanimously felt that the example was poorly chosen, since in fact one can say "I am loving this book," or the like, as in the following example: "You know that book you gave me for Christmas? Well, I'm really loving it!" Or, "Dr. Cook, I'm really loving this class!" One of them suggested that the language was changing to allow statives to violate the aspectual rule. I suggested this was probably not the case, but was unable, on the fly, to satisfactorily account for the progressive use of "love" except by vaguely saying that it was being used in a different sense in these cases. We had to move on, and there we left it.
I kept thinking about the case, however, and have come to some further conclusions. First of all, I do think the example in IBHS was poorly chosen. A better example of stative+progressive illformedness might be something like *I am knowing the multiplication table or *I am having a new computer or *I am now owning my own home. These usages are indeed incompatible with progressivity, since these statives are not events and denote no action that can "progress" in terms of having some kind of internal temporal structure (like "I am walking the dog").
Second, the situation that IBHS likely envisaged in their sample sentence I am loving this book must have been like the sentences in the previous paragraph, indicating a non-event. For example, if someone pointed to a book on their shelves and said, "See that book with the red cover? Well, I am loving this book," that would be an example of the same kind of illformedness as "*I am owning this book."
Whence, then, the "event" reading of "loving" in I am loving this book? Under that reading, "this book" cannot mean "this object"; it has be taken as "the current process of reading this book." It can't even mean "this book that I finished last week." "Love" can only receive a non-stative reading, and be used in the progressive, when it has for its object (either explicitly or implicitly) another currently ongoing process that is itself progressive. Yet another example: consider the sentence "I am loving this week's episode of Glee." It can only be used of watching this week's episode of Glee (let's say you are on the phone with your friend), and not of the script or performances or plot. Not every stative can participate in this alternation, however.
The fact that Waltke & O'Connor say that the sample sentence cannot be "freely" uttered is unclear. It could mean that they were aware of counter-usages like the one discussed here (in which case they should have chosen a better example).
BIBLIOGRAPHY: The original description of stativity as incompatible with the progressive can be found in Zeno Vendler's classic article, "Verbs and Times," The Philosophical Review, Vol. 66, No. 2. (Apr., 1957), pp. 143-160. By the way, this is not cited in IBHS.