To finish reading (a book, text, etc.); to read through to the end.
その小説を昨日の夜に読み終わった。
I finished reading that novel last night.
途中で寝てしまって、まだ読み終わっていない。
I fell asleep halfway and haven't finished reading it yet.
全部読み終わるまで、感想は言わないでください。
Please don't give your opinion until you've finished reading it all.