How difficult is the Contributions? It depends on your expectations. Daniela Vallega-Neu in her essay Poetic Saying puts it like this:

When Contributions to Philosophy first appeared in 1989 after gaving been announced by Otto Pöggeler and Friedrich-Wilhelm von Herrmann as Heidegger's second major wotk after Being and Time, the critical response seemed rather more disappointed than excited. What presented itself to critics was an apparently random collection of repetitive notes, aphorisms, fragments of texts, collections of questions, or lists of words and unfinished sentences that were utterly different from the systematic exposition of Dasein given in Being and Time. And event those sections with longer passages and "complete" sentences are marked by a strange abruptness. The reader finds himself deprived of linking elements providing continuity of thought in a smotth development from one question to the next. No "concepts" are systematically introduced and developed; no didactic considerations are provided. The reader is left alone, without support and eventually exposed to the power of naked words uttering the event of beyng.

    The language of Contributions demands that the reader expose herself to a thinking that does not provide any support for familiar ways of thinking. For those that are not ready to engage in a journey along an unknown path with an uncertain destiny, Contributions must remain a random collection of fragments, a "private language" at most, cryptic in its content and unworthy of being taken seriously.
P. 66

That final phrase could also be read as: "unworthy of being, taken seriously." Is Heidegger not up to the task he earlier assigned to himself? To clear up the problem in B&T's epigraph and raise anew the question of the meaning of being? Many of Heidegger's critics don't even believe there is such a thing as being nor that it is a fit subject for philosophy--that philosophers' discussion of it is brought about by grammatical confusion. Not being taken seriously, being taken lightly, as comedy, also appears in Simon Blackburn's review of the Contributions:

What seems to be random hyphenation further dislocates, or dis-locates, any sense of being at home, or being-at-home, with the words on the page. Sometimes this results in unintended comedy: Heidegger is fond of saying that things we cannot do anything about are thrown at us, and for some pages this leads to talk of a "free-throw," giving the surprising impression that the subject of this metaphysics is basketball.

All joking aside, perhaps what is missing from so many studies of Heidegger and existentialism is comedy. Death and tragedy are well attended to, but no one appears to have examined the lighter aspects being. Plenty has been written about death, anxiety, anguish, and so on, so why has no one done a phenomenology of comedy. Presumably ontology should be behind every aspect of the world, both the tragic and the comedic. There is as much humor in breakdowns of the ready-to-hand as tragedy, if not more. What is slap-stick if not such breakdowns? And reading Ms. Vallega-Neu above, and the Contributions I am inspired to apply the cut-up method to this text, and prepared to be delighted by the unintended juxtapositions of the resulting textual mashup. It is a weakness of contemporary philsophy that it needs to take itself so seriously. The need for gravitas is probably a consequence of the imperiled status of university humanities departments in today's technological world, rather than anything intrinsic to philosophy or to the question of the meaning of being.  ¶ 6:44 AM