Abstract: A bookmark device formed of plastic has a narrow, low-profile and elongated bookmark extension, with an enlarged, wider cap portion at its upper end. The cap portion provides a cap for a removable highlighter pen which comprises an enlarged head of the bookmark device with an internal reservoir holding highlighter fluid and a highlighter tip for marking text. In a preferred embodiment the cap and the highlighter head lie essentially entirely to one side of the plane of the bookmark extension, so that in use, the bookmark can always be oriented one way or the other between the pages of the book without increasing the profile of the book. In one embodiment the bookmark device can be part of a set of components including additional highlighter heads, for replacement purposes and for providing different highlighter colors. The device is conveniently used for highlighting while reading.