diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,8 @@
 # Revision history for stack-all
 
+## 0.2.1 (2021-04-30)
+- if stack fails, print the ~/.stack snapshot path for reference
+
 ## 0.2 (2021-04-03)
 - better error messages when reading snapshot option/arg (TristanCacqueray)
 - search parent dirs for stack project dir, like stack
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -9,28 +9,71 @@
 `stack-all` by default runs `stack build` over
 recent Stackage LTS major versions and Nightly
 (current default is nightly, lts-17, lts-16, lts-14,... , lts-11)
-corresponding to latest major ghc minor verions.
+corresponding to latest major ghc minor versions,
+using the stack's `--resolver` option.
 
-Note that stack-all will automatically use `stack-ltsXX.yaml`, even for older lts releases: eg say you have `stack-lts13.yaml` in your project, then it will also be used for building lts-12 (unless you have a `stack-lts12.yaml` config file of course).  (Other versioned stack.yaml filenames like stack-ghc-8.8.yaml are not supported currently.)
+### Overriding stack.yaml
+`stack-all` can use `stack-ltsXX.yaml` files to override the default `stack.yaml`
+file for particular lts major versions. Note that a `stack-ltsXX.yaml` file
+will also be used for earlier lts major versions until
+another `stack-ltsYY.yaml` file is found.
 
-You can specify the oldest working LTS for a project with `stack-all -o lts-13` or set it in a `.stack-all` file containing:
+For example if you have `stack-lts14.yaml` and `stack-lts12.yaml` files
+in your project,
+then `stack.yaml` will be used as normal to build nightly, lts-17 and lts-16,
+but `stack-lts14.yaml` will be used for building lts-14 and lts-13,
+and `stack-lts12.yaml` will be used for lts-12, lts-11 (and earlier).
+Since `stack-all` overrides the resolver with `--resolver lts-XX`
+the exact minor lts version specified in the `stack*.yaml` files
+doesn't actually matter: `stack-all` always uses the latest minor release of
+the lts major version according to Stackage.
+
+(Other versioned stack.yaml filenames like stack-ghc-8.8.yaml
+are not currently supported.)
+
+### Configuring the oldest lts to build
+You can configure the oldest working LTS major version for your project
+by running for example `stack-all -c -o lts-13` which generates a `.stack-all`
+project config file like this:
 ```
 [versions]
-# lts-12 foo-bar too old
+# lts-12 too old
 oldest = lts-13
 ```
-which can be created with `stack-all -c -o lts-13`.
+(the comment line can be used to document why the older lts doesn't work).
+This specifies that the oldest lts version to build for is lts-13.
 
-You can also pass stack commands and options on the command line: eg
+### Specifying lts versions
+You can abbreviate `lts-XX` args to `ltsXX` on the commandline.
+
+There are `--oldest`  and `--newest` options to specify the range of
+lts versions to build over:
+
+You can specify the oldest major lts to build for with eg `stack-all -o lts13`.
+Otherwise if not configured the default oldest lts is currently `lts-11`.
+
+Similarly you can specify the newest lts version to build from with
+`stack-all -n lts16`. (The default is to build from nightly.)
+
+Alternatively, one can give one or more explicit lts major versions to build for
+as arguments: eg `stack-all lts14` if you only wish to build that version.
+
+### Running other stack commands
+By default `stack-all` just runs the stack `build` command over lts versions.
+
+You can also specify the stack command to run and its options on the commandline:
+eg
 ```
-$ stack-all test
+$ stack-all test --no-rerun-tests
 ```
-will run `stack test` over the LTS versions, etc (instead of `stack build`).
+will run `stack test` over the LTS versions instead.
 
 Happy stack building!
 
 ## Install
-Run `stack install` or `cabal install` in the source.
+The project is released on Hackage.
 
-## Contribute or discuss
-at https://github.com/juhp/stack-all
+You can also build from source with `stack install` or `cabal install`.
+
+## Collaboration
+The project is hosted at https://github.com/juhp/stack-all under a BSD license.
diff --git a/src/Main.hs b/src/Main.hs
--- a/src/Main.hs
+++ b/src/Main.hs
@@ -166,11 +166,16 @@
         case sort (filter (snap <=) configs) of
           [] -> []
           (cfg:_) -> ["--stack-yaml", showConfig cfg]
-      args = ["-v" | debug] ++ ["--resolver", showSnap snap] ++
-             config ++ command
+      opts = ["-v" | debug] ++ ["--resolver", showSnap snap] ++
+             config
   if debug
-    then debugBuild args
-    else cmd_ "stack" args
+    then debugBuild $ opts ++ command
+    else do
+    ok <- cmdBool "stack" $ opts ++ command
+    unless ok $ do
+      putStr "\nsnapshot-pkg-db: "
+      cmd_ "stack" $ "--silent" : opts ++ ["path", "--snapshot-pkg-db"]
+      error' $ "failed for " ++ showSnap snap
   putStrLn ""
   where
     showConfig :: Snapshot -> FilePath
diff --git a/stack-all.cabal b/stack-all.cabal
--- a/stack-all.cabal
+++ b/stack-all.cabal
@@ -1,8 +1,8 @@
 name:                stack-all
-version:             0.2
+version:             0.2.1
 synopsis:            CLI tool for building across Stackage major versions
 description:
-        Build your Haskell project over Stackage major versions.
+        Build your Haskell project over Stackage major LTS versions.
 license:             BSD3
 license-file:        LICENSE
 author:              Jens Petersen <juhpetersen@gmail.com>
@@ -16,7 +16,7 @@
                      ChangeLog.md
 cabal-version:       1.18
 tested-with:         GHC == 8.0.2, GHC == 8.2.2, GHC == 8.4.4, GHC == 8.6.5,
-                     GHC == 8.8.4, GHC == 8.10.2, GHC == 9.0.1
+                     GHC == 8.8.4, GHC == 8.10.4, GHC == 9.0.1
 
 source-repository head
   type:                git
@@ -27,7 +27,7 @@
   other-modules:       Paths_stack_all
   build-depends:       base < 5,
                        config-ini,
-                       directory,
+                       directory >= 1.2.5,
                        extra >= 1.6.15,
                        filepath,
                        process,