"I have endeavored to follow up scholarly theological books with shorter, generally accessible works. I have kept myself accountable to the injunction: 'That which cannot be said simply is perhaps not worth saying at all.' As such, I followed up Theology of Hope (1967) with the popular-level work, In the End — The Beginning (2004); my Christology, The Way of Jesus Christ (1990), with Jesus Christ for Today’s World (1994); and The Spirit of Life (1992) with The Source of Life (1997)."
I have all six of these books and noticed when comparing them how much shorter the "accessible works" are.
Speaking of numbers, I have more like three dozen Moltmann books, some of which are on my Kindle. I'd say the shorter versions would be a good place to start, if you are new to reading books by Jürgen Moltmann. Wikipedia has a full list of his books.
- Theology of Hope has 342 pages,
while In the End — The Beginning has only 192 pages.
- The Way of Jesus Christ has 388 pages,
while Jesus Christ for Today’s World has only 152 pages.
- The Spirit of Life has 358 pages,
while The Source of Life has only 148 pages.