There are not many PhD dissertations in this collection, but occasionally I come across one that I find personally interesting as well as relevant for our field and quite readable. Moussette's work fits that profile. The general topic is haptic interaction and what I find valuable about it is how he explores the field through digital sketching, yielding knowledge contributions towards a more general understanding of haptics as well as concrete design exemplars for appropriation into the repertoires of other designer-researchers.
Available for free download from http://www.simplehaptics.se