Bottom line (real library, 2,692 EPUBs; lower is better)

Bookends is small in absolute terms, but not free.

Compared with my previous round

Mixed, with no plugin better across the board. Each plugin is compared with Stock of the same round (the rounds ran on different setups, so absolute times aren't comparable):

• ZenOS: retained heap above Stock fell from +23 to +8 MiB; library render 1.4x → 1.2x Stock. Restart, open and close got relatively slower.
• SimpleUI: library render improved (~3.5x → 2.4x Stock), heap about the same (+56 → +52 MiB), closing a book much slower (2.7x → 8.1x).
• Bookshelf: close to Stock in both rounds (+5 → +6 MiB), but its own shelf pages slower (84 → 133 ms default, 26 → 38 ms animation off).
• VOS: about the same, a bit heavier.

Several releases and the setup changed at once, so this shows direction, not cause.

Correction

In my first post Project:Title looked like the clear winner. That was my mistake: the harness never switched it to its cover list, while everything else ran covers. With covers on it is about as light as Stock (14 MiB, fastest book open at 98 ms) but its sort change is slower. A cover list costs roughly +20 ms on a sort change and +17 ms on first render for every stack that uses it.

Thanks, Andy

Caveat

This is an emulator comparison, not Kindle hardware: 100 ms here is not 100 ms on a Kindle (no E-Ink delays, different CPU/storage, no real memory pressure). The memory figure is one forced-GC checkpoint per stack. I also included my own unpublished minimal plugin as a reference point; it was indistinguishable from Stock.

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For scale: the same full matrix takes about 20 minutes on a Mac emulator. On the real Paperwhite it’s roughly 6–8.5 hours, plus charging and cooldown pauses. If I find that much time, there’ll be a real-device benchmark soon; this is just for context.