John Macquarrie FBA TD was a Scottish-born theologian and philosopher. Timothy Bradshaw has described Macquarrie as "unquestionably Anglicanism's most distinguished systematic theologian in the second half of the twentieth century."
(Jim Cook’ review) Macquarrie’s lucidly written book discusses existentialist theology both in general terms and specifically with respect to the Protestant (Lutheran) theology of the great German theologian and teacher, Rudolf Bultmann.
Macquarie accomplishes this task by means of comparing and contrasting Bultmann’s theology with the key concepts developed by Martin Heidegger in his masterwork, Being and Time, which was first published in 1927. Heidegger and Bultmann were friends who both taught at the University of Marburg between 1923-28. Bultmann was the older of the two by about 5 years, although they both died within months of each other in 1976.
Macquarie is a good guide to Heidegger’s Being and Time and he provides the reader with clear explanations of many of Heidegger’s difficult (not to say obscure) concepts such as: anxiety, being-in-the-world, facticity, care, conscience, time, historicity, and death; and the ideas of authenticity and inauthenticity. Macquarie was later to become the senior editor/translator of Sein und Zeit (Being and Time) into the English language in 1962; a translation that is still regarded as the most definitive scholarly translation of this seminal work by Heidegger.
Macquarie also provides an excellent and balanced introduction to Bultmann’s theology of the New Testament, describing how Bultmann pursues a sort of phenomenology of faith through demythologizing its key passages, especially those written by Paul and John.
Today, of course, any work comparing Heidegger and Bultmann would spend more time on their lengthy correspondence (covering the years 1925 - 1975), and some of Heidegger’s later works; as well, it would have to address Heidegger’s involvement with Nazism.
Regardless, Macquarrie’s 1955 book remains of value in any attempt to understand either thinker.