With thanks to Mark Goodacre for mentioning this:
William Wrede’s classic Das Messiasgeheimnis in den Evangelien; Zugleich ein Beitrag zum Verständnis des Markusevangeliums (1901) is now available online at archive.org: Das Messiasgeheimnis in den Evangelien As usual with archive.org, you can download as PDF, read online in flipbook format and so on. Also available on archive.org are Wrede’s Paulus and The Origin of the New Testament. The latter is also now available on Google Books in toto, including for download as a Google ebook, so you can even read it on your phone: The Origin of the New Testament.
Of course you won’t want to read it on your Phone. Phones are for talking people, look up the word phone!
Seriously, Wrede is must (w)reading for anyone doing work in the NT.