Eric Herber has written a new IDS book in German called Informix 11.5
as part of the Entwickler Press Schnell+Kompakt series.

The book runs to 148 pages and covers the following topics: Installation und Konfiguration (Installation and Configuration) Fein-Tuning der Instanz (Fine-tuning of the instance) Sicherung und Wiederherstellung (Backup and restore) Lasterverteilung und Hochverfügbarkeit (Low and high distributions(?) IDS-Dienstprogramme (IDS Utilities)

Eric has been kind enough to provide a translation of the back cover:

Informix Dynamic Server (IDS) has established itself as a cult database
in the market. Its fans admire the unmatched reliability, the easy and
compact administration as well as the impressive speed. In versions 11 and
11.5 IBM has massively invested in the development of IDS technology. IDS
11.5 allows the creation of highly available, scalable database-clusters on
top of cost-efficient hardware with intelligent load balancing.
IDS solves the challenges of critical OLTP environments, which requre "round
the clock" availability, with its usual easy administration
and configuration. Also IDS is the first choice as an integrated database, delivered as
part of the application. Learn more about the
sophisticated technology of IBM IDS in this book.

There is an additional a description of the book, including an errata and sample pages at Informix Zone.