I'm thinking about purchasing the authors' works Microfungi on Land Plants and Microfungi on Miscellaneous Substrates. The price is fairly high though and the original versions were printed in the 80's, so they are not the most up-to-date works. 

I'm sure there have been many taxonomic changes, but if one is just interested having a decent description of a large number of ascos (Helotiales especially, but descriptions of e.g. pyrenos would also be nice), do you think these are still worth buying?

I've been searching for a relatively comprehensive book about ascos and this pair is the only one that seems interesting to me. Not an over-abundance of literature in this field...