The goal of this anthology is a noble one. I think appraisal theories of emotion are broadly correct, and it's a fascinating and crucial question what "appraisal" amounts to. It makes intuitive sense to approach this question by associating "appraisal" with our basic folk psychological word "belief. But I think the authors of these papers totally botch this project. I'll first briefly explain the gist of appraisal theories of emotion, then address what I see lacking in this anthology, and finally speculate on why this project got so botched.
On appraisal theories of emotion, emotions are to be understood in terms of a complex set of psychological processes, which are responsible for the production and maintenance of an emotional state. These processes are such that the same emotional state can endure over a period of time, over which different things may come to preoccupy the role of its intentional object. Moreover, these processes are such that there are conceptually isolable stages of the course of producing and maintaining an emotional state. These stages need not occur in a temporally sequential order. For example, there are the stages of the activation of autonomic nervous activity, appraisal of the environment, and motivational readiness towards actions fitting in light of the environmental situation and our needs. Appraisal is to be defined in terms of a causal role integrated within the causal roles played by other elements within these emotion processes, and so various kinds of psychological activity could fulfill this role, such as judgment and perception alike.
For example, certain philosophers have argued that the startle response is an emotion. The startle response is reflexively triggered by some loud sounds. Many animals are capable of it, humans, sloths, and squirrels alike. Startle might seem to be an emotion, insofar as it is accompanied by a characteristic facial expression and autonomic nervous activity, and it makes us attend to our environment in a certain way. Our eyes and mouth squeeze shut, and we are primed to look out for potentially threatening features of our environment. A feature of the startle response is that it lacks any cognitive element, and it is non-intentional; so if this were an emotion, it'd pose challenge to the mainstream thought that emotions are intentional, or about things.
Under the appraisal framework of understanding emotion, the startle response is just a stage of a larger emotion process; it amounts to the activation of a certain sort of autonomic nervous activity. Once this stage of the emotion process is set, we will inevitably go through the other stages that culminate in an actual emotion. One of these other stages necessarily involve our apprising our environment; given evolutionary considerations, it is plausible that appraisal will necessarily involve that, once we identify the causes of this autonomic nervous activity, we take them to be either real or unreal. These causes thereby serve as the intentional object of an emotion, which is taken to be either real or unreal.
But this collection of papers was not informative, and sometimes even misleading. My primarily complaint is that most of these papers felt like a waste of space; the authors take their dandy time to talk about a simple idea in terms of many paragraphs. Moreover, this lengthy writing does not add empirical detail or clarity; often the authors just use vocabulary that is unnecessarily complicated and talk about the same thing in unnecessarily various ways (e.g., in chapter 2, the authors explain the basic idea that an emotion directed towards a cluster of remembered events can make us confuse these events with one another and fail to notice their significant differences; they do this over many pages, when this idea could be expressed in a single paragraph).
Why do the authors so mess up this important project? Authors across papers often do not define belief and emotion, and sometimes their implicit definitions differ from one another's. I think in order to make progress on this project, it is important to explicitly dwell upon how we ought to define these terms. If we implicitly presume, for example, that belief is a propositional attitude, this will make us notice only certain questions to be asked about the relationship between emotion and belief, and bar us from others (e.g., this rules out questions concerning how emotion might bear on non-propositional but nevertheless informational states). I'd like to look into whether psychologists have done much work on defining belief; philosophers have, and it'd be interesting to see how the projects between these disciplines might differ.
I admire Frijda's work generally. I'd recommend readers interested in this subject to, instead of looking into this anthology, just go to his major papers (or the empirical papers by his collaborator Klaus Scherer).