Yes, I would go with what you've already have since it would take time to prep something new. There's nothing wrong with a free guidebook, that sounds good to me. How long have you been offering this guidebook? If you've been pushing it for a while and still have 5 subs, there might be something amiss with the messaging, framing or presentation of the guidebook.
It could be hard to tell though so don't immediately go looking for something wrong it's just something to consider if it hasn't been working well and that's why you're asking. Alternatively, it could just be that you're not pushing enough traffic at it, it's hard to measure without enough data.