The Succubus by Evald Flisar — a Slovenian novelist writing in English about Ljubljana and the country's transition from socialist Yugoslavia to independence. Flisar captures the disorientation of a city changing character faster than its inhabitants can process.
The Encyclopaedia of the Dead by Danilo Kiš — the Belgrade-born writer (with Slovenian and Hungarian ancestry) is the greatest literary figure of the former Yugoslavia. This short story collection, though not set in Ljubljana, is the best single introduction to the moral and imaginative world of the region. Understanding the background that shaped Slovenia makes Ljubljana more legible.
Architectural Guide to Ljubljana by Bogo Zupančič — for anyone interested in Plečnik and the city's extraordinary twentieth-century architecture, this systematic guide covers the built fabric street by street. Not a page-turner, but irreplaceable if you want to understand what you are looking at.