Su'cuy, vod!

Download Calibre: https://calibre-ebook.com/ or (clickable link).

Calibre is about the best ebook management and control program around and it's free. You can get it for windows, mac, and linux or download and run it from a portable storage device (I'm using a windows PC).

Install it and run it. It's gonna ask you where you want to put your library. Dealer's choice on this one. I recommend your internal drive (and then back up to external/cloud), but YMMV.

If you want to keep fanfic separate from the rest of your ebooks, you can create multiple libraries. I do, and my libraries are creatively named 'Books' and 'Fic'.

Customise Calibre

Now you're gonna install some plugins. Go to Preferences on the menu bar (far right), click its little side arrow, then choose 'Get plugins to enhance Calibre'.

At the top right of the box that pops up is 'Filter by name'. The plugins you want to get are:

EpubMerge

FanFicFare

Install them one at a time. It will ask you where you want them. I recommend 'the main bar' and 'the main bar when device is attached' (should be selected by default). When you're done, close and reopen Calibre.

The plugins you just installed should appear on the far right of the toolbar, but if you can't see one or both of them, fear not! Just click Preferences (the button, not the side arrow), then Toolbars and Menus (in the 'Interface' section) then choose the main toolbar from the drop down menu. That will let you add and remove things - I suggest getting rid of Donate, Connect Share, and News. That'll leave you room to add your new plugins to the menu bar.

(Do donate, though, if you can afford it. This is a hell of a program.)

Now you're ready to start saving your fave fanfic!

Saving fanfic

I'll go through both methods I use, but pick whatever makes you happy (and/or works best for what you're downloading).

ETA: if the fics are locked you can't easily use FanFicFare. Skip down to the next section. (It does ask for a username/password if you try and get a locked fic, but it's never worked for me - I had to edit the personal.ini in the configuration options, and even then it skips locked fics in a series.)

Calibre and FanFicFare

You can work from entirely within Calibre using the FanFicFare plugin. Just click its side arrow and pick from the menu. The three main options I use are download from URL, make anthology from a webpage, and update story/anthology.

Download from URL: pick Download from URL (or just click the FanFicFare button) and paste the fic's URL into the box (if you've copied it to your clipboard, it will be there automatically). You can do more than one fic at a time - just paste the URLs in one after the other (each on a new line). When you're done, make sure you have the output format you want and then go.

Make Anthology Epub From Web Page: if you want a whole series as a single ebook, pick Anthology Options, then Make Anthology Epub From Webpage. Paste the series URL into the box (if you've copied it to your clipboard, it will be there automatically), click okay when it displays the story URLs, check your output format and go.

Update series/anthology: if you downloaded an unfinished fic or series and the author updates, you can automatically add the update to your ebook. Just click on the ebook in Calibre, open the FanFicFare menu using its side arrow, and select either Update Existing FanFic Books or Anthology Options, Update Anthology epub. Okay the URLs and/or the output format, then go.

Any fic downloaded using FanFicFare will be given an automatically generated Calibre cover. You can change the cover and the metadata by right clicking on the title and picking edit metadata. You can do it individually, to change the cover or anything else specific to that ebook, or in bulk, which is great for adding a tag or series name to multiple fics. Make sure you generate a new cover if you change the metadata.

Browser plugins, Calibre, and EpubMerge

You can also use a browser addon/plugin to download from AO3. I use FicLab (Firefox/Chrome), but I believe there's others. FicLab: https://www.ficlab.com/ (clickable link).

FicLab puts a 'Save' button next to fic when you're looking at a list of fics, eg search results, series page, author's work list etc. Just click the 'Save' button, adjust the settings, and download the fic. You can also use it from within the fic by clicking the toolbar icon and running it.

FicLab is great if you're reading and come across a fic you want to save. It also generates a much nicer (IMO) cover than Calibre.

You can add the downloaded fic to Calibre (just drag and drop) or save it wherever. The advantage to dropping it into Calibre is that all your fic stays nicely organised, you can adjust the metadata, and you can easily combine fics.

Combining fics

You can combine multiple fics into an anthology using EpubMerge. This is great if you want a single ebook of an author's short fics, or their AUs, or their fics in a specific ship that aren't part of a series. (It only works on epubs, so if you've saved as some other format, you'll need to convert using Calibre's Convert books button.)

Select the ones you want to combine, click EpubMerge, adjust the order if necessary, and go.

The cover of the merged epubs will be the cover of the first fic in the merge list. You can add a new cover by editing the metadata and generating a new cover.

Combing with FanFicFare

You can also combine nonseries fics using FanFicFare's Make Anthology ePub from URLs option by pasting the individual fic URLs into the box.

Where there's more than a few fics, I find it easier to download them with FicLab and combine them with EpubMerge, and I prefer keeping both the combined and the individual versions of fic, but again YMMV.

Reconverting and Converting

Once I'm done fussing, I reconvert the ebook to the same format, to ensure everything is embedded in the file. Is this necessary? YMMV, but it's a quick and easy step that does zero harm.

If you don't want your final ebook to be an epub, just convert it to whatever format you like.

Disclaimers

Save fanfic for your own personal enjoyment/offline reading/safeguarding against the future. If it's not your fic, don't distribute it, or upload it to other sites, or otherwise be a dick. Especially if the author deletes it. Respect their wishes and their rights.

This may work on other fanfic sites, eg FFN, but I've never tried so I don't know.

If you download a fic, do leave the author a kudo or a comment; you'll make them so happy.