In the first two booklets the process of experience is analyzed in depth and the total absence of control over it is confirmed. This should be more than enough to understand the first noble truth and by understanding this, the other three are understood.
The following booklets deal with various topics. In Samyutta 16 on Kassapa, a curious anecdote occurs. In SN 16.9 "Jhānas and Paranormal Abilities" the Buddha reviews all his meditative attainments of the Buddha by comparing himself with his predecessor the Buddha Kassapa. This is why he adds to each achievement "and Kassapa too". This would not be of great importance if it were not that Kassapa, the disciple of the Buddha in charge of overseeing the Discipline of the Sangha of the bhikkhus, upon hearing it understood that he was referring to himself, not to the eponymous Buddha, which will provoke in him a conceit that will lead him, in the following two suttas, to two shameful fights of greengrocers with Ānanda with desolate results for the bhikkhunīs.
The Book of the Factors of Clinging to Existence is the third of the five books of the Interwoven Discourses. It is named after its first saṁyutta which is the dominant one both in length and importance, since it deals with a key aspect of the teachings.
The analysis of the factors of clinging to existence represents the logical level systematization of experience and is key to understanding suffering and describes how we are chained to Samsara. Experience involves five processes: qualia, emotional reaction, perception, conditional situation and cognition. The first is the process related to sense inputs and the other four are the processes of conceptualization.