Used lovefool's files: https://nyaa.si/view/1768037
Since the audiobooks have 上, 中, and 下 I used those versions. I found them on Z-Library.
I bought 戦物語 myself.
番外編 includes 佰物語オリジナルドラマCD シナリオブック and 化物語 アニメコンプリートガイドブック
There is no epub version of 混物語 I can find and I don't want to buy it.